Wednesday, October 19, 2011

Most Common HTTP Error Codes

1xx CODES - INFORMATION ONLY
100 - Continue; partial request received
101 - OK to switch protocols
102 Processing
103 Checkpoint
122 Request-URI too long


2xx CODES - SUCCESS
200 - OK; all requested info returned
201 - Created; request filled
202 - Accepted; request received
203 - Source unknown; 3rd party info
204 - No new content; nothing to send
205 - Reset content; OK to clear form
206 - Request only partially filled

3xx CODES - REDIRECTION
300 - Header for 3xx codes
301 - Moved permanently; use new URL
302 - Moved temporarily; use same URL
303 - Redirected
304 - Not modified; use cached copy
305 - Use proxy; URL is provided
306 Switch Proxy
307 Temporary Redirect
308 Resume Incomplete


4xx CODES - FAILURE
400 - Did not understand request
401 - Password required
402 - Payment required
403 - Request refused
404 - Not found (Fix available)
406 - Content type not acceptable
407 - Browser must authenticate
408 - Timed out; send again
409 - Update conflict with explanation
410 - Not found; resource gone
411 - Content length missing
412 - Conditions on request failed
413 - Request too long to process
414 - Resource address too long
415 - Unsupported media type; bad format

5xx CODES - SERVER ERRORS
500 - Internal error
501 - Cannot fill request
502 - Cannot process gateway request
503 - Overloaded or service over limits
504 - Gateway or proxy server timed out
505 - HTTP version not supported

Code 404 Info and Repair

The 404 or Not Found error message is a HTTP standard response code indicating that the client was able to communicate with the server, but the server could not find the URL address (web page) that was requested.

A 404 error should not be confused with "server not found" or similar errors, in which a connection to the destination server could not be made at all. A 404 error sometimes indicates that the requested resource might be available again in the future.

If you prefer to skip the extra information provided for you here, you can do so by simply going directly to the How to Fix Error 404
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Receiving a 404 error after you attempt to access a web page via a specific link is equivalent to sending a letter in the mail to a person who doesn't exist at that address or to an address the post office doesn't recognize, or itself no longer exists. Hence, the infamous "Return to Sender" stamped on the return envelope many of us have received in the postal mail at one time or another.

An error 404 message is generated by a bad link, meaning that either the link information itself is corrupted or the most common reason is that the web page itself no longer exists.

Before we get into discussing how to repair the error message itself, look over the following definitions. You will need to know these definitions in order to fully understand the error 404 explanation.

HTTP Status Code 404 (Error) Glossary

Client:
 is typically a user's computer (yours, mine, your neighbors laptop etc)

Client program:
An application running in a user's computer. Usually the operating system (aka windows, Linux)

Request:
The information that your web browser (Internet Explorer, Chrome, Firefox etc) sends to a Web server. The information packet contains the details of what the browser wants and will accept back from the server. The request header (as the request is called) also contains the type, version and capabilities of the web browser that is making the request so that server returns only compatible data.

Upon receipt of the request header, the server will return what is called a HTTP response header to the client that is attached to the file(s) being sent.

Web browser
Internet Explorer, Chrome, Firefox etc

Web server:
See HTTP Server below

HTTP Server
The term "Web server" often refers only to the HTTP server software in the machine, which provides the Web site functionality. HTTP is the protocol of the Web, and HTTP server software, such as Microsoft's IIS and the open source Apache server, accepts requests from the user's browser and responds by sending back HTML documents (Web pages) and files. It also executes scripts that reside in the server (CGI scripts, JSPs, ASPs, etc.), which perform functions such as database searching and credit card authorization. See IIS and Apache.

HTTP Return Codes
Any messages, status code,error or otherwise that are returned to the users web browser (aka clients program) from any given Web server are called "status codes". The codes report any information about a page request that comes back to the client.

A status code that is returned from the Web server (HTTP server) to the client's browser which is obviously viewed on the client's computer screen, indicates the status of the page (URL) request and reports errors and necessary information so that the client software can respond. 

Error 404
A HTTP "error 404" message appears when the web page that was requested is no longer available or restricted from your access or restricted from being viewed on that particular web server.

The 404 error message page can be modified by the site's Webmaster to a more graphically-friendly message depending upon how involved the website builder wants to get just to make a simple error message appear more attractive.

Though error message creation is really beyond the scope of this particular article, the latter paragraph does touch base on the importance of creating an attractive error message web page especially if you want your visitors to want to keep coming back.

Despite today's technology being what it is most links to most Web pages (URL) are static in nature. In other words, if a web page is no longer available for whatever the reason, an error message is a web servers only means of communicating the problem to you.

There is software that exists that probes each link on any given website to determine whether or not the target page for those links still exist. The software can not automatically search for new working web pages for that specific link if that page no longer exists because it has not been given any other pre-defined reference addresses to search.

I suppose a clever coder can easily create a program that would be able to use the non-existent URL as a starting point to automatically begin a new search for the replacement web page. But that would require that the webmaster give the new page an address that was within a predetermined set of search parameters. So for now these pages will have to remain static.

The most common result of a dead link is a 404 error, which indicates that the web server responded, but the specific page could not be found.


Not surprising that the masses have found an amusing way to make use out of something as annoying as broken web page links. Apparently the "404" term has become a hip slang synonym for meaning "clueless" in the United Kingdom.

Though the slang usage of the term was confined to London and other surrounding urban areas, there are other parts of Europe and the US that are using "404" to refer to useless politicians, low grade weed, heavy cut cocaine and even to mean when someone is a no show or not at home.


Novice Computer User Solution (completely automated):

1) Download (error 404) repair utility.
2) Install program and click Scan button.
3) Click the Fix Errors button when scan is completed.
4) Restart your computer.

Advanced Computer User Solution (manual fixing):


1) Start your computer and log on as an administrator.
2) Click the Start button then select All Programs, Accessories, System Tools, and then click System Restore.
3) In the new window, select "Restore my computer to an earlier time" option and then click Next.
4) Select the most recent system restore point from the "On this list, click a restore point" list, and then click Next.
5) Click Next on the confirmation window.
6) Restarts the computer when the restoration is finished.