Originally the motherboard was powered by one 20-pin connector. An ATX power supply provides a number of peripheral power connectors, and (in modern systems) two connectors for the motherboard: a 4-pin auxiliary connector providing additional power to the CPU, and a main 24-pin power supply connector, an extension of the original 20-pin version.

Four wires have special functions:

• PS_ON# or Power on is a signal from the motherboard to the power supply. When the line is connected to ground (by the motherboard), the power supply turns on. It is internally pulled up to +5 V inside the power supply.
• PWR_OK or Power good is an output from the power supply that indicates that its output has stabilized and is ready for use. It remains low for a brief time (100–500 ms) after the PS_ON# signal is pulled low.
• +5 V_SB or +5 V standby supplies power even when the rest of the supply lines are off. This can be used to power the circuitry that controls the Power On signal.
• +3.3 V sense should be connected to the +3.3 V on the motherboard or its power connector. This connection allows for remote sensing of the voltage drop in the power supply wiring.

Generally, supply voltages must be within ±5% of their nominal values at all times. The little-used negative supply voltages, however, have a ±10% tolerance. There is a specification for ripple in a 10 Hz–20 MHz bandwidth:

ATX power supply revisions

Original ATX

ATX, introduced in late 1995, defined three types of power connectors:

• 4-pin “Molex connector” — transferred directly from AT standard: +5 V and +12 V for P-ATA hard disks, CD-ROMs, 5.25 inch floppy drives and other peripherals.
• 4-pin Berg floppy connector — transferred directly from AT standard: +5 V and +12 V for 3.5 inch floppy drives and other peripherals.
• 20-pin Molex Mini-fit Jr. main motherboard connector — new to the ATX standard.
• A supplemental 6-pin AUX connector providing additional 3.3 V and 5 V supplies to the motherboard, if needed. This was used to power the CPU in motherboards with CPU voltage regulator modules which required 3.3 volt and/or 5 volt rails and could not get enough power through the regular 20-pin header.

The power distribution specification defined that most of the PSU’s power should be provided on 5 V and 3.3 V rails, because most of the electronic components (CPU, RAM, chipset, PCI, AGP and ISA cards) used 5 V or 3.3 V for power supply. The 12 V rail was only used by fans and motors of peripheral devices (HDD, FDD, CD-ROM, etc.).

The original ATX power supply specification was little revised until 2000.

ATX12V 1.x

While designing the Pentium 4 platform in 1999/2000, the standard 20-pin ATX power connector was found insufficient to meet increasing power-line requirements; the standard was significantly revised into ATX12V 1.0 (ATX12V 1.x is sometimes inaccurately called ATX-P4). ATX12V 1.x was also adopted by AMD Athlon XP and Athlon 64 systems.

ATX12V 1.0

The main changes and additions in ATX12V 1.0 (released in February 2000) were:

• Increased the power on the 12 V rail (power on 5 V and 3.3 V rails remained mostly the same).

• An extra 4-pin mini fit JR (Molex 39-01-2040), 12-volt connector to power the CPU.  Formally called the +12 V Power Connector, this is commonly referred to as the P4 connector because this was first needed to support the Pentium 4 processor.

Before the Pentium 4, processors were generally powered from the 5V rail. Later processors operate at much lower voltages, typically around 1 V, and some draw over 100 A. It is infeasible to provide power at such low voltages and high currents from a standard system power supply, so the Pentium 4 established the practice of generating it with a DC-to-DC converter on the motherboard next to the processor, powered by the 4-pin 12V connector.

ATX12V 1.1

This is a minor revision from August 2000. The power on the 3.3 V rail was slightly increased, and other lesser changes made.

ATX12V 1.2

A relatively minor revision from January 2002. The only significant change was that the −5 V rail was no longer required (it became optional). This voltage was used only on some old systems with certain ISA add-on cards.

ATX12V 1.3

Introduced in April 2003 (a month after 2.0). This standard introduced some changes, mostly minor. Some of them are:

• Slightly increased the power on 12 V rail.
• Defined minimal required PSU efficiencies for light and normal load.
• Defined acoustic levels.
• Introduction of Serial ATA power connector (but defined as optional).
• The −5 V rail is prohibited.

ATX12V 2.x

ATX12V 2.x brought a very significant design change regarding power distribution. On analyzing the then-current PC architecture’s power demands it was determined that it would be much cheaper and more practical to power most PC components from 12 V rails, instead of from 3.3 V and 5 V rails.

ATX12V 2.0 

The above conclusion was incorporated in ATX12V 2.0 (introduced in February 2003), which defined quite different power distribution from ATX12V 1.x:

• The main ATX power connector was extended to 24 pins. The extra four pins provide one additional 3.3 V, 5 V and 12 V circuit.
• The 6-pin AUX connector from ATX12V 1.x was removed because the extra 3.3 V and 5 V circuits which it provided are now incorporated in the 24-pin main connector.
• Most power is now provided on 12 V rails. The standard specifies that two independent 12 V rails (12 V₂ for the 4 pin connector and 12 V₁ for everything else) with independent overcurrent protection are needed to meet the power requirements safely (some very high power PSUs have more than two rails, recommendations for such large PSUs are not given by the standard).
• The power on 3.3 V and 5 V rails was significantly reduced.
• The power supply is required to include a Serial ATA power cable.
• Many other specification changes and additions.

ATX12V v2.01

This is a minor revision from June 2004. An errant reference for the -5V rail was removed. Other minor changes were introduced.

ATX12V v2.1

This is a minor revision from March 2005. The power was slightly increased on all rails. Efficiency requirements changed. Added 6-pin connector for PCIe graphics cards, that aids the PCIe slot in the motherboard, delivering 75 watts.

ATX12V v2.2

Another minor revision. Added 8-pin connector for PCIe graphics cards, that delivers another 150 watts.

ATX12V v2.3

Effective March 2007 and current as of 2011.  Recommended efficiency was increased to 80% (with at least 70% required), and the 12 V minimum load requirement was lowered. Higher efficiency generally results in less power consumption (and less waste heat), and the 80% recommendation brings supplies in line with new Energy Star 4.0 mandates.  The reduced load requirement allows compatibility with processors that draw very little power during startup.  The absolute over-current limit of 240VA per rail was removed, allowing 12V lines to provide more than 20A per rail.

• Purchase this Product Here
• Features
• System Requirements
• Review
• Drivers and Downloads

Features

• Switchable key pad – Flexible design, choose right side or left side configuration. Switch between standard key pad and macro pad in gaming mode.
• Two-color adjustable backlighting dial – Keyboard keys are red, and key pad and Macro keys are amber in Game mode. Lighting dial adjusts the brightness of the keyboard and key pad.
• Macro keys – Up to 30 programmable keys that can allow up to 90 programmable options with an assigned gaming profile.
• Mode switching – Manually toggle the keyboard from standard mode to either of two gaming modes. LEDs show the selected mode.
• Cruise Control – Use Cruise Control to continue an action without having to hold down the key or keys assigned to the action. You can use Cruise Control with up to four keys at a time.* (* Cruise Control does not work with programmable macro keys.)
• In-game macro record button – Record any sequence of keystrokes—even standard chat messages. Macros are stored on your hard drive and can be easily shared.
• Device Stage – Quickly and easily access common tasks, including product information, registration, settings and more for popular devices such as cell phones, cameras, printers, and mouse, keyboard and webcam products.
• Automatic profile switching – When a game or application profile is assigned using the software, the keyboard detects the game or application you are running and applies your custom profile to the application.
• WASD gaming keys – Have front-face lighting for enhanced visibility.
• Media keys – Play/Pause, Previous Track, Next Track, and Mute.
• 3 year warranty

System Requirements

• Requires a PC that meets the requirements for and has installed one of these operating systems: Windows® 7/Windows Vista®/Windows XP
• 100MB Hard Drive Space
• CD Drive
• Powered USB Port
• Internet access required for software installation

Review

With the Sidewinder X6 gaming keyboard, Microsoft aims at the serious PC gamer who demands programmable keys and customized functionality for various situations in gaming. The keyboard’s unique removable keypad is definitely a luxury that some may find useful in terms of ergonomics. The X6 is a slick black keyboard that measures 20.2 inches wide and 9.22 inches deep. It does take up quite a bit of room, so be prepared to clear some space in order for it to rest comfortably. Its thick rubber feet are sure to keep it from slipping during gaming sessions. One of the main features of the X6 boasts is a unique, removable number pad. Depending on your preference, you can connect the keypad to either side of the keyboard via a magnetic contact. Say you’re a southpaw who’s more comfortable with the keypad to the left; the X6 can adjust to suit you. The keyboard also has an adjustable backlight display that illuminates every single key. Standard keys glow red while the keypad and programmable buttons have an amber hue to them. The intensity is adjustable via a large knob at the top of the keyboard, something like you’d find on a car dashboard. The X6 has a number of hot-key features that enhance the overall gaming experience. Once you install the bundled software, you can customize the 30 “S” keys found on the detachable keypad along with a row parallel to the left-most side of the standard keyboard. You can also store these keys in one of three save states, which gives you a way to switch between a work mode and play mode, for example. A convenient button on the top row allows you to switch through these profiles at any time. Through the included software, you can also assign specific configurations to particular games. These custom layouts will automatically load along with the game they’re bound to. Not only can the keyboard learn three “modes,” it can record macros on the fly. During gameplay, you can press a button that will log any sequence of keystrokes you wish. In addition, there’s an interesting “cruise-control” button that lets you teach the keyboard a specific keystroke (up to four buttons pressed simultaneously) which it will then repeat for you whenever you’d like. While some might call this cheating, it’s certainly useful for mundane tasks you may have to do in a role-playing or real-time-strategy game. If you’re playing games in Vista, a dedicated Game Explorer button will allow you to instantly navigate and choose which game to launch. Unfortunately, this feature won’t work with Windows XP. The Sidewinder X6 has other vanity controls as well. Adjacent to the backlight dimmer knob, you get a volume control knob. The keyboard also has media control buttons, as well as a dedicated calculator key. In terms of comfort, the Sidewinder didn’t really wow us with any sort of advanced ergonomics. In fact we actually found it quite irritating during everyday typing. The built-in hard plastic wrist pad provides no cushioning, nor is it removable, which prevents you from using a wrist rest you’re more comfortable with. Also, you get no drop-down feet to raise the height of the keyboard. Almost every keyboard we’ve ever seen has the ability to change its height and the fact that it’s not included here feels like an oversight, given that it’s such an easy feature to add. We did, however, like the feel of the keys and their relatively silent operation; the X6 has a certain unique smoothness to it that we really enjoyed. While we didn’t quite enjoy the X6 for everyday typing, the experience we had while using it to play games was a lot better. Even though its angle isn’t adjustable, the default positioning of the board is great for resting your fingers at the default “WASD” key positions. (source)

Drivers and Downloads

• Technical Data Sheet (v8.0.225.0)
• IntelliType Pro 8.0 – Windows 7 64 Bit (v8.0.225.0)
• IntelliType Pro 8.0 – Windows 7 32 Bit (v8.0.225.0)
• IntelliType Pro 8.0 – Windows Vista 64 Bit (v8.0.225.0)
• IntelliType Pro 8.0 – Windows Vista 32 Bit (v8.0.225.0)
• IntelliType Pro 6.31 – Windows XP 64 Bit (v6.31.258.0)
• IntelliType Pro 8.0 – Windows XP 32 Bit (v8.0.225.0)

Simply go to the Steam website and “take the test”".  The website will automatically detect the system’s hardware configuration and after verifying the presence of GeForce graphics, will allow the download of the FREE games, including:

• Portal: First Slice
• Half-Life 2: Deathmatch
• Half-Life 2: Lost Coast
• Peggle Extreme

Visit www.steampowered.com/nvidia to get your free downloads before this offer ends!

Aside from being annoying, Vista’s constant check for low drive space uses system resources which can slow Windows down.

Follow the easy steps to turn off the low disk space checks in Windows Vista.

Note: Changes to the Windows Registry are made in these steps. Take great care in making only the registry key changes described below. I recommend backing up the registry keys you’re modifying in these steps as an extra precaution.

regedit

The games included are: World of Warcraft, StarCraft II Beta and Warcraft III. If you play any of these games, you’ll want to roll your drivers back to earlier versions until this is fixed, unless you want to replace a video card within the next few days.

To find out what version drivers you’re using:

- Right-click on your desktop
- Click NVIDIA Control Panel
- When the Control Panel opens, in the bottom left corner there should be a “System Information” link; click this
- Your Driver version should be in the Details portion

Windows XP: http://www.nvidia.co…96.21_whql.html
Windows XP 64-bit: http://www.nvidia.co…96.21_whql.html
Windows Vista/7 32-bit: http://www.nvidia.co…96.21_whql.html
Windows Vista/7 64-bit: http://www.nvidia.co…96.21_whql.html

More information can be found on threads such as these:
http://forums.nvidia…howtopic=161525
http://forums.nvidia…howtopic=161503

Source: http://wow.curse.com/articles/wow-en-news/690242.aspx

Computer Laptop Battery Care and Usage Tips for getting more from a notebook battery.

1. Turn off Wi-Fi and BlueTooth – Most laptops have shortcut keys to instantly disable wireless networking.

2. Don’t play computer games, music or DVD movies – Multimedia activities drain laptop batteries.

3. Disconnect all external device like PC Card modems, Firewire, USB devices and optical drives. Use the notebook touchpad instead of an external mouse.

4. Adjust your screen brightness – Dimming your display saves battery power.

5. Tweak Windows Power Options – Choose a Laptop power scheme that turns off the notebook monitor and hard disk after 10 minutes of inactivity.

6. Decrease or mute the Laptop Speaker Volume.

7. Turn off all scheduled tasks.

8. Turn off Auto-save features in Microsoft Office and other applications.

9. If your PC has a built-in wireless card, turn it off or disable it when not in use.

10. Programs that are run from a CD or DVD can be copied to and run from the hard drive, which typically consumes less power than an optical drive.

Here are some more tips to improve your notebook’s battery life:

1. If you do not use your laptop for extended periods of time (a week or more), remove the battery pack from the laptop.

2. Do not expose the battery to high heat or freezing temperatures. Do not leave your battery in your car in the summer. Hot batteries discharge very quickly, and cold ones can’t create as much power.

3. Make sure to plug your laptop charger adapter into a UPS and not directly into a power outlet or surge protector.

4. If you have a nickel-metal hydride battery, completely drain and recharge the battery once a month to maximize its capacity to hold a charge.

5. Fully charge new battery packs before use. New pack needs to be fully charged and discharged (cycled) a few times before it can condition to full capacity.

6. For laptops that work as Desktop Replacement, the battery should be re-installed every 3-4 weeks and allowed to fully discharge.

7. Leaving a battery in a laptop while using an electrical outlet for long periods of time will keep the battery in a constant state of charging up and that will reduce the life cycle of the battery.

Battery-saving sleep modes: Should I use Stand By or Hibernate

Standby mode
Use standby to save power when you will be away from the computer for a short time while working – your monitor and hard disks turn off, all applications and open files are stored in RAM. When you want to use the computer again, it comes out of standby quickly, and your desktop is restored exactly as you left it.

Hibernation Mode
Use hibernation to save power when you will be away from the computer for an extended time while working – your computer shuts down to save power but first saves everything in memory on your hard disk. When you restart the computer, your desktop is restored exactly as you left it.

When you choose Start, Turn off Computer in Windows XP, your options are Stand By, Turn Off, and Restart. To hibernate, place the cursor over Stand By, then hold down Shift and click.

Microsoft Office 2010, codenamed Office 14, is a productivity suite for Microsoft Windows and Mac OS X, and is the successor of Microsoft Office 2007 for Microsoft Windows and Microsoft Office 2008 for Mac OS X. Office 2010 includes extended file compatibility, user interface updates, and a refined user experience. It will be available for Windows XP SP3 (32-bit), Windows Vista SP1, Windows 7 and Mac OS X. With the introduction of Office 2010, a 64-bit version of Office will be available for the first time, although only for the Windows Vista and Windows 7 operating systems.

Microsoft has confirmed that Office 2010 will be released in the first half of 2010 (around June), and a public beta was made available in November 2009.

Office 2010 will mark the debut of free online versions of Word, Excel, PowerPoint, and OneNote, which will work in popular web browsers (Internet Explorer, Mozilla Firefox, Google Chrome, and Apple Safari). A new edition of Office, Office Starter 2010, will replace the current low-end home productivity software, Microsoft Works.

Microsoft’s update to its mobile productivity suite, Office Mobile 2010, will also be released for Windows Phones running Windows Mobile 6.5.

Features

According to an article published in InfoWorld  in April 2006, Office 2010 will be more “role-based” than previous versions. The article cites Simon Witts, corporate vice president for Microsoft’s Enterprise and Partner Group, as claiming that there would be features tailored to employees in “roles such as research and development professionals, sales persons, and human resources.” Borrowing from ideas termed “Web 2.0″ when implemented on the Internet, it is likely that Microsoft will incorporate features of SharePoint Server in Office 2010.

Microsoft Office 2010 will implement the ISO/IEC compliant version of Office Open XML (OOXML) which was standardized as ISO/IEC 29500:2008 in March 2008, though will also have the option of implementing as a setting the ISO/IEC compliant version of OpenDocument Format (ODF) v1.1, beyond 1.0 which was standardized as ISO/IEC 26300:2006 in May 2006.
New features are also said to include a built-in screen capture tool, a background removal tool, a protected document mode, new SmartArt templates and author permissions. The 2007 “Office Button” will be replaced with a menu button that leads to a full-window file menu, known as Backstage View, giving easy access to task-centered functions such as printing and sharing. A refined Ribbon interface will be present in all Office applications, including Office Outlook, Visio, OneNote, Project and Publisher. Office applications will also have functional jumplists  in Windows 7, which would allow easy access to recent items and tasks relevant to the application.

Confirmed features of Office 2010 include:

• Refined Ribbon interface and Backstage View across all applications
• Background Removal Tool
• Letter Styling
• The Word 2007 Equation editor will become common to all applications, replacing MS Equation 3.0
• New SmartArt templates
• New text and image editing effects
• Screen Capturing and Clipping tools
• Live collaboration functions
• Jumplists in Windows 7

Office Edition Comparison

Office 2010 Starter Edition

In November 2009, Microsoft released a private technical preview (beta) of the Starter Edition to select people. Office 2010 Starter edition is a scaled-down edition of Office 2010 that only includes Microsoft Word Starter 2010 and Microsoft Excel Starter 2010.

There are significant differences between the Starter Edition and other editions of Microsoft Office, such as:

• Included components: Office 2010 Starter edition includes only Microsoft Word Starter 2010 and Microsoft Excel Starter 2010.
• Reduced functionality: Office 2010 Starter edition only provides basic support for macros. It is unable to open the following file types: .xla, .xlam, .dsn, .mde, .accde, .odc, and .udl. Add-ins are also not supported.
• Supported operating system: Office 2010 Starter edition only runs on Windows Vista and Windows 7.
• License: Office 2010 Starter edition is only available to original equipment manufacturers (OEM) for preloading on Windows PCs. Users who purchase these products however, are allowed to load Office 2010 Starter edition on a USB drive and run it on any computer.
• Inclusion of advertisement: Office 2010 Starter edition displays advertisements.

Office 2010 Starter edition is to replace Microsoft Works.

Office Web Apps

Microsoft plans to offer a free web-based version of its Office productivity suite, known as Office Web Apps, that will debut with the release of Office 2010. Office Web Apps will include online versions of Word, Excel, PowerPoint and OneNote. The web apps will allow sharing and collaboration of documents and files and also feature user interfaces similar to their desktop counterparts. It was also noted that the release does not include full functionality of the Office Web Apps and did not include the OneNote Web App nor the ability to edit Microsoft Word documents, however, these functionalities are enabled in the public beta release of late 2009.

Office Mobile 2010

The office suite for Windows Mobile by Microsoft will also be updated together with Office 2010. Windows Mobile 6.5 will be required to run Office Mobile 2010. New features include:

• Presentation Companion: The add-on to PowerPoint Mobile allows users to control a presentation through their Windows Phone and display speaker notes.
• Conversation View: Outlook Mobile will thread related emails into a group for easier reading and management
• SharePoint Workspace Mobile: The new application will allow users to sync documents from SharePoint servers directly to their Windows Phone for offline viewing and editing.
• Support for new content in Office 2010 such as SmartArt graphics and charts

It is unknown if Microsoft will release an upgrade to Office 2010 for existing Windows Phones running Windows Mobile 6.5.

Intel Core i7 is Intel’s brand name for several families of desktop and laptop 64-bit x86-64 processors using the Intel Nehalem micro-architecture. It is a successor to the Intel Core 2 brand. The Core i7 identifier was first applied to the initial family of processors  codenamed Bloomfield introduced in 2008. In 2009 the name was applied to Lynnfield and Clarksfield models. Prior to 2010, all models were quad-core processors. In 2010, the name was applied to dual-core Arrandale models, and the upcoming Gulftown Core i7-9x0X Extreme processor will have six hyperthreaded cores.

Intel representatives state that the moniker Core i7 is meant to help consumers decide which processor to purchase as the newer Nehalem-based products are released in the future.  The name continues the use of the Intel Core brand.  Core i7, first assembled in Costa Rica,  was officially launched on November 17, 2008  and is manufactured in Arizona, New Mexico and Oregon, though the Oregon (PTD, Fab D1D) plant has already moved to the next generation 32 nm process.

Processor cores

The initial Core i7 processors released were codenamed Bloomfield branded as Core i7-9xx along with their Xeon 3500-series counterparts. As of 2009, they are Intel’s high-end Desktop processors, sharing the Socket 1366 platform with the single and dual-processor server processors.

Lynnfield is the second processor sold under the Core i7 brand, while at the same time being sold as Core i5. Unlike Bloomfield, it does not have a QPI interface but directly connects to a southbridge using a 2.5 GT/s Direct Media Interface and to other devices using PCI Express links in its Socket 1156. Core i7 processors based on Lynnfield have Hyper-Threading, which is disabled in Lynnfield-based Core i5 processors.

Clarksfield is the mobile version of Lynnfield and available under the Core i7 Mobile brand, as part of the Calpella platform. It was released at the Intel Developer Forum on September 23, 2009.

The second mobile Core i7 processor family will be Arrandale, sold as the Core i7-6xx processors and featuring an integrated graphics processing unit but only two processor cores, half of Clarksfield. Clarkdale (microprocessor), the desktop version of Arrandale, will not be sold as Core i7, but only as Core i3 and Core i5.

Gulftown will be the extreme version of the Core i7, with up to 6 hyperthreaded cores, 12 MB of cache, Turbo Boost and Intel QuickPath connection bus. The first release will be the Core i7 980X in Q1 2010.

Codename (main article)	Logo	New Logo	Brand name (list)	L3 Cache	Socket	TDP	Min. feature size	I/O Bus	Release Date
Gulftown (Unreleased)			Core i7-980X Extreme Edition	12 MiB	LGA 1366	130 W	32 nm	QuickPath	Mar 2010
Bloomfield			Core i7-9xx Extreme Edition	8 MiB			45 nm		Nov 2008
			Core i7-9xx
Lynnfield			Core i7-8xx		LGA 1156	95 W		Direct Media Interface	Sep 2009
			Core i7-8xxS			82 W			Jan 2010
Clarksfield			Core i7-9xxXM Extreme Edition		µPGA-989	55 W			Sep 2009
			Core i7-8xxQM			45 W
			Core i7-7xxQM	6 MiB
Arrandale			Core i7-6xxM	4 MiB		35 W	32 nm	Direct Media Interface, Integrated GPU	Jan 2010
			Core i7-6xxLM			25 W
			Core i7-6xxUM			18 W

With a wide range of ever-improving offerings, Logitech’s Harmony line of PC-programmable remote control have gobbled up a large share of the universal remote-control market in recent years. Still, there are plenty of people who just don’t like the fact that you need to do the bulk of the setup duties for those units while they’re tethered to a computer. For that crowd, the URC Digital R50 will be a breath of fresh air. (URC is short for “Universal Remote Control,” the aptly-named company that also makes remotes under the Home Theater Master brands, as well as many of the “generic” remotes that are packaged with cable boxes and other devices.)

The Digital R50 combines a color information screen with a standard control wand full of DVR-friendly buttons, and uses a built-in programming wizard that makes it fairly straightforward to replace the remotes of up to 18 component devices. It is 9 inches long by 2.25 inches wide; once you load the 4 AA batteries (included), it feels substantially solid in your hand. It has 44 hard, rubber keys, plus a five-way directional pad. The top quarter of the unit is a 2-inch, 176×220 color screen flanked by eight contextual buttons, the functions of which change depending upon what’s on the screen (the bottom two are usually “page back” and “page forward,” allowing you to move between multiple screens). Screen brightness and resolution is excellent, and the unit’s device icons and channel logos look great.

Below that are the volume and channel controls. The directional pad dominates the center of the remote; it’s encircled by DVR-friendly “guide, “menu,” “info,” and “exit” keys. Below that are the video-transport controls (play, pause, fast-forward, and rewind, as well as dedicated “skip back” and “skip forward” buttons). The bottom quarter of the remote is a standard 12-digit keypad. (DTV fans will appreciate that there’s a dedicated “dash” key, perfect for punching in digital channels.)

In a perfect world, we’d prefer the video-transport controls to be closer to the center, and we wouldn’t have gone with the hourglass key layout that pushes some keys too far to the periphery. But all in all, it’s a good key layout–better than the Philips Prestigo SRU8010, which made the mistake of isolating the video-transport keys at the bottom. All of the R50 keys are also completely backlit–just click the button on the remote’s right-hand side, and the resulting amber glow provides easy visibility, even in complete darkness.

The “main” key underneath the screen could be better called “home.” Press it for 5 seconds, and you’ll enter the setup mode. Main options include basic and advanced setup, as well as favorite channels and preferences, which are the user settings, such as screen brightness and low-battery warning settings. Using the basic setup option, you can get most of your devices programmed in rapid succession. Follow the onscreen prompts, and the built-in wizard guides you straight through the process. Most mainstream devices will be built into the Digital R50′s internal database. Once you choose a device button on the screen (up to 18 devices can be controlled), pick the type of device (TV, audio, DVR, VCR, and so forth) and the manufacturer, and the remote will automatically begin cycling through the codes. Once the device powers off, it asks you to double check the codes, and you can lock them in or try again. We tried several products–TVs, AV receivers, iPod clock radios, and game consoles–and the Digital R50 nailed every one without a problem.

Purchase this product here.

• HTTP Error 400: Bad request
• HTTP Error 401: Unauthorized
• HTTP Error 402: Payment Required
• HTTP Error 403: Forbidden
• HTTP Error 404: Not Found
• HTTP Error 405: Method Not Allowed
• HTTP Error 406: Not Acceptable
• HTTP Error 407: Proxy Authentication Required
• HTTP Error 408: Request Timeout
• HTTP Error 409: Conflict
• HTTP Error 410: Gone – Permanently Not Available
• HTTP Error 411: Length Required
• HTTP Error 412: Precondition Failed
• HTTP Error 413: Request Entity Too Large
• HTTP Error 414: Request URI Too Long
• HTTP Error 415: Unsupported media type
• HTTP Error 416 Requested Range not satisfiable
• HTTP Error 417 Expectation failed
• HTTP Error 500: Internal Server Error
• HTTP Error 501: Not Implemented
• HTTP Error 502: Bad Gateway
• HTTP Error 503: Service Unavailable
• HTTP Error 504: Gateway Timeout
• HTTP Error 505: HTTP Version Not Supported

Introduction to errors

Any client (e.g. your Web browser) goes through the following cycle when it communicates with your Web server:

• Obtain an IP address from the IP name of your site (your site URL without the leading ‘http://’). This look-up (conversion of IP name to IP address) is provided by domain name servers (DNSs).
• Open an IP socket connection to that IP address.
• Write an HTTP data stream through that socket.
• Receive an HTTP data stream back from your Web server in response. This data stream contains status codes whose values are determined by the HTTP protocol. Parse this data stream for status codes and other useful information.

An error may occur in any of the above steps.

HTTP Error 400 Bad request

The Web server (running the Web site) thinks that the data stream sent by the client (e.g. your Web browser) was ‘malformed’ i.e. did not respect the HTTP protocol completely. So the Web server was unable to understand the request and process it.

There is a low-level problem in the client or the Web server or both. 95% of the time this is because of a problem on the client system e.g. there is something unstable on your PC running the Web browser.

• Is your PC secure ?. If your PC is not well-protected, then all kinds of problems may occur – including HTTP 400 errors. If you run Windows, stay uptodate with automatic security updates from Microsoft and possibly consider getting a registry cleaner. Always have good anti-virus and spyware protection. Invest in a hardware firewall if you can afford one. Be sensible surfing the Web – block pop-up windows and avoid bad sites. If your PC security is compromised, then Web traffic out from your PC to the Internet may be secretly corrupted by malware (spyware, viruses, etc.) running on your PC. This can be difficult for you to detect.
• Have you installed web-based software ?. Some social networking and games sites ask you to download and run software on your PC so you can interact with other people on the Internet directly (without using your Web browser). This software, if badly written or even criminal, can corrupt all HTTP traffic from your PC. Getting rid of that defective software can be difficult. At worst you may have to reinstall your operating system again (possibly losing all your personal data on your PC if you do not have backup).
• How stable is your Internet connection ?. If you have recently changed ISPs or your ISP is very slow or unreliable, then Web traffic from your PC out to any site on the Internet may be corrupt. Your ISP may have reconfigured some of their setup (e.g. introduced new proxy servers or cacheing) that is causing some instability. A possible sign of problems here is if you can not easily browse the Web site of your ISP. You can also try to check that the Web site you are actually visiting is the one you think you are visiting. For example, you may have a DNS problem. You can check this using a ‘ping’ test. A DNS problem may be caused by your ISP or may be on your own system e.g. in a ‘hosts’ file.
• Do you get the error on more than one Web site ?. If you get the error on lots of Web sites, this indicates the problem is on your PC, not on those sites.
• Do you get the error using more than one browser ?. If you have two or more Web browsers installed on your PC and the behavior is not the same (one Web browser gives an HTTP 400 error visiting a site, another Web browser does not give the 400 error visiting the same site), then one of your browsers may be defective. Try to find an upgrade or security fix for the problem browser. If you recently changed some configuration options in the problem browser, try reversing the change to see if that helps.
• Do you get the error on big Web sites ?. If you get the problem on quite a small site, visit some of the bigger sites like Amazon, Ebay, Google, Microsoft and Yahoo. If you get the problem only on small sites, it indicates a problem with only those sites or the traffic from your PC to those sites.
• Do you get the error on simple URLs ?. If you get a problem with a long complicated URL (such as http://www.xxx.com?PHPrequest=643&value=dres&cookies=No) but not with a shorter simpler URL for the same site (such as http://www.xxx.com), this can indicate a problem with the Web server on the site you are trying to visit. This is not conclusive evidence, but is a good starting point. Contact the owners of the Web site and describe the problem to them. You may find for example the problem occurs with POST methods (you are both submitting data to the Web site and retrieving data from the Web site), but not with GET methods (you are only retrieving data from the Web site).
• Do you have a cache problem ?. Try clearing your cookies, browser cache and browsing history in your Web browser. Disable or remove any third-party cacheing or ‘web accelerator’ software you installed. Then try rebooting your PC and any firewall/router you use to connect to the Internet. That may not fix the error, but at least may eliminate any problem due to old settings on your PC.
• What has changed since you started getting the HTTP 400 problem ?. In general terms, think about what has changed on your PC since you first started seeing the problem. This may cover any of the items mentioned above. Work backwards and see if undoing those changes makes any difference.

So there are a lot of things that you can check on your own PC. If you contact the owners of the Web site giving you the HTTP 400 error and they say “We have lots of other users who do not have your problem – so there must be something wrong with your PC”, they are right most of the time – and you can not expect them to be interested in fixing your own PC problems. However if they know there is a problem with their Web site, they should hopefully tell you so and tell you when they plan to fix the problem.

HTTP Error 401 Unauthorized

The Web server (running the Web site) thinks that the HTTP data stream sent by the client (e.g. your Web browser) was correct, but access to the URL resource requires user authentication 1) which has not yet been provided or 2) which has been provided but failed authorization tests. This is commonly known as “HTTP Basic Authentication”. The actual authentication request expected from the client is defined in the HTTP protocol as the WWW-Authenticate header field.

Generally this error message means you need to log on (enter a valid user ID and password) somewhere first. If you have just entered these and then immediately see a 401 error, it means that one or both of your user ID and password were invalid for whatever reason (entered incorrectly, user ID suspended etc.).

Each Web Server manages user authentication in its own way. A security officer (e.g. a Web Master) at the site typically decides which users are allowed to access the URL. This person then uses Web server software to set up those users and their passwords. So if you need to access the URL (or you forgot your user ID or password), only the security officer at that site can help you. Refer any security issues direct to them.

If you think that the URL Web page *should* be accessible to all and sundry on the Internet, then a 401 message indicates a deeper problem. The first thing you can do is check your URL via a Web browser. This browser should be running on a computer to which you have never previously identified yourself in any way, and you should avoid authentication (passwords etc.) that you have used previously. Ideally all this should be done over a completely different Internet connection to any you have used before (e.g. a different ISP dial-up connection). In short, you are trying to get the same behavior a total stranger would get if they surfed the Internet to the Web page.

If this type of browser check indicates no authority problems, then it is possible that the Web server (or surrounding systems) have been configured to disallow certain patterns of HTTP traffic. In other words, HTTP communication from a well-known Web browser is allowed, but automated communication from other systems is rejected with an 401 error code. This is unusual, but may indicate a very defensive security policy around the Web server.

Error 402: “Payment Required”

The purpose of this message is to inform you that your request for service could not be completed due to service closure based on account delinquency. The account will be re-activated once the responsible party has paid any remaining overdue balance.

The original intention was that this code might be used as part of some form of digital cash or micro-payment scheme, but that has not happened, and this code has never been used.

HTTP Error 403 Forbidden

The Web server (running the Web site) thinks that the HTTP data stream sent by the client (e.g. your Web browser) was correct, but access to the resource identified by the URL is forbidden for some reason.

This indicates a fundamental access problem, which may be difficult to resolve because the HTTP protocol allows the Web server to give this response without providing any reason at all. So the 403 error is equivalent to a blanket ‘NO’ by the Web server – with no further discussion allowed.

By far the most common reason for this error is that directory browsing is forbidden for the Web site. Most Web sites want you to navigate using the URLs in the Web pages for that site. They do not often allow you to browse the file directory structure of the site.

This URL should fail with a 403 error saying “Forbidden: You don’t have permission to access /…………. on this server”. This is because the Web site deliberately does not want you to browse directories – you have to navigate from one specific Web page to another using the hyperlinks in those Web pages. This is true for most Web sites on the Internet – their Web server has “Allow directory browsing” set OFF.

You first need to confirm if you have encountered a “No directory browsing” problem. You can see this if the URL ends in a slash ‘/’ rather than the name of a specific Web page (e.g. .htm or .html). If this is your problem, then you have no option but to access individual Web pages for that Web site directly.

It is possible that there should be some content in the directory, but there is none there yet. For example if your ISP offers a ‘Home Page’ then you need to provide some content – usually HTML files – for the Home Page directory that your ISP assigns to you. Until the content is there, anyone trying to access your Home Page could encounter a 403 error. The solution is to upload the missing content – directly yourself or by providing it to your ISP. Once the content is in the directory, it also needs to be authorized for public access via the Internet. Your ISP should do this as a matter of course – if they do not, then they have missed a no-brainer step.

If the entire Web site is actually secured in some way (is not open at all to casual Internet users), then an 401 – Not authorized message could be expected. It is possible, but unlikely, that the Web server issues an 403 message instead.

Some Web servers may also issue an 403 error if they at one time hosted the site, but now no longer do so and can not or will not provide a redirection to a new URL. In this case it is not unusual for the 403 error to be returned instead of a more helpful error. So if you have recently changed any aspect of the Web site setup (e.g. switched ISPs), then a 403 message is a possibility. Obviously this message should disappear in time – typically within a week or two – as the Internet catches up with whatever change you have made.

If you think that the Web URL *should* be accessible to all and sundry on the Internet and you have not recently changed anything fundamental in the Web site setup, then an 403 message indicates a deeper problem. The first thing you can do is check the URL via a Web browser. This browser should be running on a computer to which you have never previously identified yourself in any way, and you should avoid authentication (passwords etc.) that you have used previously. Ideally all this should be done over a completely different Internet connection to any you have used before (e.g. a different ISP dial-up connection). In short, you are trying to get the same behavior a total stranger would get if they surfed the Internet to the Web page URL.

If this type of browser check indicates no authority problems, then it is possible that the Web server (or surrounding systems) have been configured to disallow certain patterns of HTTP traffic. In other words, HTTP communication from a well-known Web browser is allowed, but automated communication from other systems is rejected with an 403 error code. This is unusual, but may indicate a very defensive security policy around the Web server.

HTTP Error 404 Not found

The Web server (running the Web site) thinks that the HTTP data stream sent by the client (e.g. your Web browser) was correct, but simply can not provide the access to the resource specified by your URL. This is equivalent to the ‘return to sender – address unknown’ response for conventional postal mail services.

This error is easily shown in a Web browser if try a URL with valid domain name but invalid page e.g. http://www.ibm.com/aaaaaaaaa.html.

For top level URLs (such as www.isp.com), the first possibility is that the request for the site URL has been directed to a Web server that thinks it never had any pages for the Web site. This is possible if DNS entries are fundamentally corrupt, or if the Web server has corrupt internal records. The second possibility is that the Web server once hosted the Web site, but now no longer does so and can not or will not provide a redirection to another computer which now hosts the site. If the site is completely dead – now effectively nowhere to be found on the Internet – then the 404 message makes sense. However if the site has recently moved, then an 404 message may also be triggered. This is also a DNS issue, because the old Web server should no longer be accessed at all – as soon as global DNS entries are updated, only the new Web server should be accessed.

For low-level URLs (such as www.isp.com/products/list.html), this error can indicate a broken link. You can see this easily by trying the URL in a Web browser. Most browsers give a very clear ’404 – Not Found’ message.

Provided that the Web site is still to be found somewhere on the Internet, 404 errors should be rare. For top level URLs, they typically occur only when there is some change to how the site is hosted and accessed, and even these typically disappear within a week or two once the Internet catches up with the changes that have been made. For low-level URLs, the solution is almost always to fix the Web pages so that the broken hypertext link is corrected.

HTTP Error 405: Method Not Allowed

The HTTP protocol defines methods to indicate the action to be performed on the Web server for the particular URL resource identified by the client (e.g. your Web browser). The methods are as follows:

• OPTIONS: Find out the communication options available for a particular URL resource. Allows the client to determine the options and/or requirements associated with a resource, or the capabilities of a server, without a specific action involving transfer of data.
• GET: Retrieve the information identified by the URL resource e.g. GET a particular Web page or image. The most common method by far.
• HEAD: Identical to GET except that the server returns header information only, not the actual information identified by the URL resource. Useful to obtain meta-information about the entity implied by the request without transferring the entity-body itself. Often used to test hypertext links for validity, accessibility, and recent modification.
• POST: Submit data to the Web server such as 1) post a message to a bulletin board, newsgroup or mailing list, 2) provide input data – typically from a CGI form – to a data-handling process, 3) add a record directly to a database.
• PUT: Set (place/replace) the data for a particular URL to the new data submitted by the client. For example, upload a new Web page to a server.
• DELETE: Remove the data associated with the URL resource. For example, delete a Web page.
• TRACE: Run a remote, application-layer loop-back of the request message. Effectively a ‘ping’ which tests what data the Web server is receiving from the client.
• CONNECT: Reserved for use with tunneling (e.g. SSL) via a proxy server. This method is defined only for HTTP version 1.1, not the earlier version 1.0.

All Web servers can be configured to allow or disallow any method. For example if a Web server is ‘read-only’ (no client can modify URL resources on the Web server), then it could be set up to disallow the PUT and DELETE methods. Similarly if there is no user input (all the Web pages are static), then the POST method could be disallowed. So 405 errors can arise because the Web server is not configured to take data from the client at all. They can also arise if the client does not have sufficient authority to the particular URL resource identified on the request.

405 errors often arise with the POST method. You may be trying to introduce some kind of input form on the Web site, but not all ISPs allow the POST method necessary to process the form.

All 405 errors can be traced to configuration of the Web server and security governing access to the content of the Web site, so should easily be explained by your ISP.

HTTP Error 406 Not acceptable

A client (e.g. your Web browser) can indicate to the Web server (running the Web site) the characteristics of the data it will accept back from the Web server. This is done using ‘accept headers’ of the following types:

• Accept: The MIME types accepted by the client. For example, a browser may only accept back types of data (HTML files, GIF files etc.) it knows how to process.
• Accept-Charset: The character sets accepted by the client.
• Accept-Encoding: The data encoding accepted by the client e.g. the file formats it understands.
• Accept-Language: The natural languages (English, German etc.) accepted by the client.
• Accept-Ranges: Whether the client accepts ranges of bytes from the resource i.e. a portion of the resource.

If the Web server detects that the data it wants to return is not acceptable to the client, it returns a header containing the 406 error code.

This error occurs very infrequently in Web browsers, because most browsers will accept any data returned from the Web server.

If the client is not a Web browser, then anyone can only investigate the problem by looking at the Accept headers generated by the client system and the data stream returned by the Web server. If you do not have access to the source code for these systems, the only thing you can do is refer the problem to technical support people at the companies that developed the systems.

HTTP Error 407 Proxy authentication required

The Web server (running the Web site) thinks that the HTTP data stream sent from the client (e.g. your Web browser) was correct, but access to the URL resource requires the prior use of a proxy server that needs some authentication which has not been provided. This typically means you must log in (enter user ID and password) with the proxy server first.

A 407 error detected via a Web browser can often be resolved by navigating to the URL in a slightly different way e.g. accessing another URL for the proxy server first. Your ISP should be able to explain the role of the proxy server in their security setup and how you should use it.

This code is similar to 401 – Unauthorized, but indicates that the client should first authenticate with a proxy server. The same discussion applies to error 407 as to error 401, except that an additional proxy server is involved for 407.

HTTP Error 408 Request timeout

The Web server (running the Web site) thinks that there has been too long an interval of time between 1) the establishment of an IP connection (socket) between the client (e.g. your Web browser) and the server and 2) the receipt of any data on that socket, so the server has dropped the connection. The socket connection has actually been lost – the Web server has ‘timed out’ on that particular socket connection. The request from the client must be repeated – in a timely manner.

408 errors are often difficult to resolve. They typically involve one-off variations in system workload or operations.

If you see persistent 408 errors, the first thing to consider is the workload on the Web server – particularly around the time the 408 errors were generated. If this is light, then you also need to consider workload on the client system. If the computer systems on both ends of the socket connection seem to be running normally, then temporary Internet surges may be to blame.

HTTP Error 409 Conflict

The Web server (running the Web site) thinks that the request submitted by the client (e.g. your Web browser) can not be completed because it conflicts with some rule already established. For example, you may get a 409 error if you try to upload a file to the Web server which is older than the one already there – resulting in a version control conflict.

Note that the conflict here is usually not related to standard Web server authority/security (for which different errors are generated), but to some application-specific conflict not defined in the HTTP protocol itself.

This error seldom occurs in most Web traffic, particularly when the client system is a Web browser. The problem can only be resolved by examining what your client system is trying to do then discussing with your ISP why that behavior is not allowed.

HTTP Error 410 Gone – Permanently Not Available

The Web server (running the Web site) thinks that the URL requested by the client (e.g. your Web browser) is no longer available from that system. This is not a ‘never heard of it’ response, but a ‘does not live here any more’ response.

The 410 error also indicates that the Web server has no forwarding address for the URL, so can provide no redirection to the new Web server. This condition should generally be considered permanent. If the Web server does not know, or has no way of knowing, whether or not the condition is permanent, the status code 404 – Not found should be used instead.

The 410 error is primarily intended to assist the task of Web maintenance by notifying the client system that the resource is intentionally unavailable and that the Web server wants remote links to the URL to be removed. Such an event is common for URLs which are effectively dead i.e. were deliberately time-limited or simply orphaned. The Web server has complete discretion as to how long it provides the 410 error before switching to another error such as 404.

The Web server does have some record of the requested URL, but now believes that this URL should be serviced by a different Web server. The 410 error indicates a complete dead-end. The URL is effectively useless, and there is no clue as to an alternative Web server or URL which might be used instead.

If the URL really should be alive, then there is something fundamentally wrong with the setup of the Web server. You should see a similar ‘not found’ message when you try to access the site using any Web browser. Refer this to the Webmaster of the Web site.

HTTP Error 411 Length required

The Web server (running the Web site) thinks that the HTTP data stream sent by the client (e.g. your Web browser) should include a ‘Content-Length’ specification. This is typically used only for HTTP methods that result in the placement of data on the Web server, not the retrieval of data from it.

This error seldom occurs in most Web traffic, particularly when the client system is a Web browser. The problem can only be resolved by examining what your client system is trying to do then discussing with your ISP why the Web server expects a ‘Content-Length’ specification.

HTTP Error 412 – Precondition failed

The Web server (running the Web site) thinks that the HTTP data stream sent by the client (e.g. your Web browser or our) included a ‘Precondition’ specification which the server detected was not met.

This error seldom occurs in most Web traffic, particularly when the client system is a Web browser. The problem can only be resolved by examining what your client system is trying to do then discussing with your ISP why the Web server fails the ‘Precondition’ specification sent by the client system.

HTTP Error 413 Request entity too large

The Web server (running the Web site) thinks that the HTTP data stream sent by the client (e.g. your Web browser) was simply too large i.e. too many bytes. What constitutes ‘too many bytes’ depends partly upon the operation being attempted. For example a request to upload a very large file (via the HTTP PUT method) may encounter a ceiling on upload file size set by the Web server.

This error seldom occurs in most Web traffic, particularly when the client system is a Web browser. The problem can only be resolved by examining what your client system is trying to do then discussing with your ISP why the Web server rejects the number of bytes sent by the client system.

HTTP Error 414 Request URI too long

The Web server (running the Web site) thinks that the HTTP data stream sent by the client (e.g. your Web browser) contains a URL that is simply too large i.e. too many bytes.

Typically Web servers set fairly generous limits on length for genuine URLs e.g. up to 2048 or 4096 characters. If your URL is particularly long, you can usually try shorter variations to see roughly where the limit is. If your long URL is indeed valid, then the Web server may need to be reconfigured to allow your URLs through. Understand that Web servers have to set some reasonable limit here, because they have to deal with badly programmed clients trying to give them huge garbage URLs.

This error seldom occurs in most Web traffic, particularly when the client system is a Web browser. The URLs in this case are typically standard hyperlinks found on Web pages. These links tend to be too large if they are simply wrong i.e. the Web page containing the link has been badly coded.

If your client system is not a Web browser, the problem can only be resolved by examining what the client is trying to do then discussing with your ISP why the Web server rejects the size of the URL sent by the client system.

HTTP Error 415 Unsupported media type

The Web server (running the Web site) thinks that the HTTP data stream sent by the client (e.g. your Web browser) identifies a URL resource whose actual media type 1) does not agree with the media type specified on the request or 2) is incompatible with the current data for the resource or 3) is incompatible with the HTTP method specified on the request.

Detecting exactly what is causing this problem can be difficult, because there a number of possible reasons. Often the request involves transfer of data from the client to the Web server (e.g. a file upload via the PUT method), in which case you need to confirm with your ISP which media types are acceptable for upload.

This error seldom occurs in most Web traffic, particularly when the client system is a Web browser.

If your client system is not a Web browser, the problem can only be resolved by examining what the client is trying to do then discussing with your ISP why the Web server rejects the media type specified by the client system.

HTTP Error 416 Requested Range not satisfiable

The Web server (running the Web site) thinks that the HTTP data stream sent by the client (e.g. your Web browser) contains a ‘Range’ request which specifies a range of bytes which can not be satisfied – because the resource being accessed does not cover this byte range. For example if the resource – an image file for example – has 1000 bytes and the Range requested is 500-1500, then it can not be satisfied.

This error seldom occurs in most Web traffic, particularly when the client system is a Web browser. The URLs in this case are typically standard hyperlinks found on Web pages, which very seldom use the ‘Range’ specification.

If your client system is not a Web browser, the problem can only be resolved by examining what the client is trying to do then discussing with your ISP why the Web server rejects the ‘Range’ specification sent by the client system. Most often this is due to a badly written client system which uses the ‘Range’ specification but disregards the total size of the resource being requested.

HTTP Error 417 Expectation failed

The Web server (running the Web site) thinks that the HTTP data stream sent by the client (e.g. your Web browser) contains a ‘Expect’ request which can not be satisfied. The Expect request is fairly generic i.e. loosely defined in the HTTP protocol. It can specify more than one expectation, each of which may be interpreted differently by different Web servers.

This error seldom occurs in most Web traffic, particularly when the client system is a Web browser. This type of Web traffic seldom uses an ‘Expect’ request.

If your client system is not a Web browser, the problem can only be resolved by examining what the client is trying to do then discussing with your ISP why the Web server fails the ‘Expect’ request sent by the client system.

HTTP Error 500 Internal server error

The Web server (running the Web Site) encountered an unexpected condition that prevented it from fulfilling the request by the client (e.g. your Web browser) for access to the requested URL.

This is a ‘catch-all’ error generated by the Web server. Basically something has gone wrong, but the server can not be more specific about the error condition in its response to the client. In addition to the 500 error notified back to the client, the Web server should generate some kind of internal error log which gives more details of what went wrong. It is up to the operators of the Web server site to locate and analyze these logs.

This error can only be resolved by fixes to the Web server software. It is not a client-side problem. It is up to the operators of the Web server site to locate and analyze the logs which should give further information about the error.

HTTP Error 501 Not implemented

The Web server (running the Web site) does not understand or does not support the HTTP method it finds in the HTTP data stream sent to it by the client (e.g. a Web browser). The methods defined by the HTTP protocol are as follows:

• OPTIONS: Find out the communication options available for a particular URL resource. Allows the client to determine the options and/or requirements associated with a resource, or the capabilities of a server, without a specific action involving transfer of data.
• GET: Retrieve the information identified by the URL resource e.g. GET a particular Web page or image. The most common method by far.
• HEAD: Identical to GET except that the server returns header information only, not the actual information identified by the URL resource. Useful to obtain meta-information about the entity implied by the request without transferring the entity-body itself. Often used to test hypertext links for validity, accessibility, and recent modification.
• POST: Submit data to the Web server such as 1) post a message to a bulletin board, newsgroup or mailing list, 2) provide input data – typically from a CGI form – to a data-handling process, 3) add a record directly to a database.
• PUT: Set (place/replace) the data for a particular URL to the new data submitted by the client. For example, upload a new Web page to a server.
• DELETE: Remove the data associated with the URL resource. For example, delete a Web page.
• TRACE: Run a remote, application-layer loop-back of the request message. Effectively a ‘ping’ which tests what data the Web server is receiving from the client.
• CONNECT: Reserved for use with tunneling (e.g. SSL) via a proxy server. This method is defined only for HTTP version 1.1, not the earlier version 1.0.

If the method in the request HTTP data stream is not one of the above, then a 501 error will result. Or the method may be valid but not actually supported by the Web server. This typically only happens for newer methods such as CONNECT when received by older Web servers.

This error should be very rare in any Web browser. It is more likely if the client is not a Web browser – particularly if the Web server is old. In either case if the client has specified a valid request type, then the Web server is either responding incorrectly or simply needs to be upgraded.

HTTP Error 502 Bad gateway

A server (not necessarily a Web server) is acting as a gateway or proxy to fulfill the request by the client (e.g. your Web browser) to access the requested URL. This server received an invalid response from an upstream server it accessed to fulfill the request.

This usually does not mean that the upstream server is down (no response to the gateway/proxy), but rather that the upstream server and the gateway/proxy do not agree on the protocol for exchanging data. Given that Internet protocols are quite clear, it often means that one or both machines have been incorrectly or incompletely programmed.

This problem is due to poor IP communication between back-end computers, possibly including the Web server at the site you are trying to visit. Before analyzing this problem, you should clear your browser cache completely.

If you are surfing the Web and see this problem for all Web sites you try to visit, then either 1) your ISP has a major equipment failure/overload or 2) there is something wrong with your internal Internet connection e.g. your firewall is not functioning correctly. In the first case, only your ISP can help you. In the second case, you need to fix whatever it is that is preventing you reaching the Internet.

If you get this problem for only some of the Web sites you try to visit then it is likely to be a problem at those sites i.e. one of their pieces of equipment is failing/overloaded. Contact the people at those sites.

HTTP Error 503 – Service unavailable

The Web server (running the Web site) is currently unable to handle the HTTP request due to a temporary overloading or maintenance of the server. The implication is that this is a temporary condition which will be alleviated after some delay. Some servers in this state may also simply refuse the socket connection, in which case a different error may be generated because the socket creation timed out.

The Web server is effectively ‘closed for repair’. It is still functioning minimally because it can at least respond with a 503 status code, but full service is impossible i.e. the Web site is simply unavailable. There are a myriad possible reasons for this, but generally it is because of some human intervention by the operators of the Web server machine. You can usually expect that someone is working on the problem, and normal service will resume as soon as possible.

Please contact the system operators of the Web site (e.g. your ISP) to determine why the service is down. They will be in a much better position to help you than we are for this type of error.

HTTP Error 504 Gateway timeout

A server (not necessarily a Web server) is acting as a gateway or proxy to fulfill the request by the client (e.g. your Web browser) to access the requested URL. This server did not receive a timely response from an upstream server it accessed to deal with your HTTP request.

This usually means that the upstream server is down (no response to the gateway/proxy), rather than that the upstream server and the gateway/proxy do not agree on the protocol for exchanging data.

This problem is entirely due to slow IP communication between back-end computers, possibly including the Web server. Only the people who set up the network at the site which hosts the Web server can fix this problem.

HTTP Error 505 – HTTP version not supported

The Web server (running the Web site) does not support, or refuses to support, the HTTP protocol version specified by the client (e.g. your Web browser) in the HTTP request data stream sent to the server.

The HTTP protocol has various versions identified as major.minor e.g. version 0.9, 1.0 or 1.1. The server is indicating that it is unable or unwilling to complete the request using the major version provided by the client – other than with this error message.

Assuming that your request identifies a valid major.minor version number (the request is not fundamentally corrupt), then this error should mostly only occur if you are trying to use version 1.0 or 1.1, but the Web server only supports the older 0.9 version.

Most Web browsers assume that Web servers support 1.x versions of the HTTP protocol. In practice very old versions such as 0.9 are little used nowadays, not least because they provide poorer security and performance than newer versions of the protocol. So if you see this error in your Web browser, the only option is to upgrade the Web server software. If version 1.x requests fail, it may well be because the Web server is supporting the 1.x protocol versions badly, rather than not supporting them at all.

The same arguments apply if your client is not a Web browser.

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