HTTP Error codes

Basically, the error codes in the 400 and 500 range are the codes that are most common to the end user:
The 400 codes are intended for cases in which the client (Mosaic, Netscape, etc) seems to have caused some sort of problem when asking the server for a html document.
The 500 codes are intended for instances when the Server software (NCSA HTTPD, Netsite, etc.) running on the site that you are contacting is having a problem sending you the html document.


Bad request 400:
This is a fairly common error and basically means that the requested document could not be sent because of syntax error in the URL (site address).


Unauthorized 401:
This is one of the most common error messages and usually means that the Server is expecting some sort of encryption id from the browser (Mosaic, Netscape, etc) and when it does not recieve it, the server issues an error message.


Forbidden 403:
The document you are requesting is "forbidden" meaning that you do not have read privlidges or are not allowed to have the page sent to you.


Not found 404:
This is the most common and is similar to the 400 error. Basically this means that the document you have requested no longer exsists or that the URL (site address) is incorrect.


Internal Error 500:
The server was unable to send the html document to you due to an internal (server software) error.


Not implemented 501:
This error occurs when for example, you have pressed the submit button on a form. The server replys with this error message because it dosen't support the feature that you have requested. This is not a real common error, but typically occurs when new features or forms are implemented.


Service temporarily overloaded 502:
The server cannot process the request due to a high load (whether HTTP servicing or other requests from users). Basically, this is the "if at first you don't suceed..." error. The solution is to try back later at a time when net load or server traffic is lower. Gateway


timeout 503:
This error is caused by the connection timing out, either due to server problems, net problems or client problems. Basically, the request for information stops because the pathway to the web server has been closed.


400 – Bad Request – You probably typed in a URL wrong, the server has no clue what you’re looking for, or you aren’t allowed to have access. Usually, it’s a matter of the URL being typing in wrong. Maybe you mixed upper and lowercase letters or something.

401 – Unauthorized Request – you tried to get to something on the web server you’re not allowed to play with. In other words, you ain’t on the party list.


403 – Forbidden – You can’t access the page. You may not have access (it may require a password), or it may be blocked from your domain.


404 – Not Found – The page you were trying to look at was not found on the server. This is probably the most common error you’ll come across. What has probably happened is that the web page you were going to has been removed or re-named.


500 – Internal error – Usually caused by a CGI error. You fill out a form, but the script used to process it is not working properly.
503 – Service Unavailable – The server may be overloaded, down, or have other similar problems. Try later.

Code	Title	Description
100	Continue
101	Switching Protocols
200	OK	The request was successful
201	Created	The request was successful and a new resource was created
202	Accepted	The request was accepted for processing, but the processing is not yet complete
203	Non-Authoritative Information
204	No Content	The server has processed the request but there is no new information to be returned
205	Reset Content
206	Partial Content
300	Multiple Choices	The requested resource is available at one or more locations
301	Moved Permanently	The requested resource has been assigned a new URL and any further references should use this new URL
302	Moved Temporarily	The requested resource resides at a different location, but will return to this location in the future
303	See Other
304	Not Modified	The requested resource has not been modified since the date specified in the If-Modified_Since header
305	Use Proxy
400	Bad Request	The server could not properly interpret the request. Normally means that either address hasn’t been entered correctly or the page no longer exists.
401	Unauthorised	The site being accessed is protected and you either entered the incorrect password or the host does not want users coming from your domain to enter.
402	Payment Required
403	Forbidden	You are not permitted to access this document. It is either password-protected or the host does not want your domain to enter.
404	Not Found	The host server can’t find the HTML document at the URL you’ve entered. Either you have mistyped the URL, the document no longer exists, or you’ve been given the wrong URL.
405	Method Not Allowed
406	Not Acceptable
407	Proxy Authentication Required
408	Request Time-Out
409	Conflict
410	Gone
411	Length Required
412	Precondition Failed
413	Request Entity Too Large
414	Request-URL Too Large
415	Unsupported Media Type
500	Internal Server Error	The server could not satisfy the request due to an internal error condition.
501	Not Implemented
502	Bad Gateway	The server received an invalid response from the server from which it was trying to retrieve information.
503	Out of Resources
504	Gateway Time-Out
505	HTTP Version not supported
	Bad File Request	The form you’re trying to access is not supported by your browser or there is an error in the form.
	Cannot Add Form Submission Result to Bookmark List	Occurs when you’ve submitted a search request and then try to save the result as a bookmark. Even though it may look like a valid address, the resulting page does not have a URL that can be reused so it can’t be added to your bookmark list.
	Connection Refused by Host	You’re not permitted to access this document either because it’s password-protected or the host doesn’t permit your domain to enter.
	Failed DNS Lookup	The URL you requested could not be translated into a valid Internet address by the domain name system. This is either a result of a mistake in the system or you could have mistakenly entered an incorrect URL
	File Contains no Data	The site you accessed doesn’t contain any Web pages on it.
	Helper Application not Found	You’re trying to load a file of a type that your browser doesn’t recognise
	Host Unavailable	The server computer that hosts this site could not be reached. The server may be offline or down for maintenance
	Host Unknown	The server you’re trying to reach is not connected, or you have lost your own connection. You may have also entered the URL incorrectly.
	Network Connection was Refused by the Server	Some servers have limits on the number of people or request they can handle at a time. If you get this message, the server is probably too busy to handle one more user.
	NNTP Server Error	This error occurs when you are trying to log on to a Usenet newsgroup. An NNTP server is part of your Internet service provider’s software, so if this error occurs the software may be malfunctioning or the newsgroup does not exist.
	Permission Denied	When connecting to an FTP site, can signify that you cannot upload to the site, download a certain file, or access a certain directory.
	Too Many Connections - Try Again Later	The limit to the number of people who can use the site at one time has been exceeded.
	Too Many Users	To avoid slow uploading and downloading rates, site administrators set a maximum number of users that can access the site at one time. Your request is one too many.
	Unable to Locate Host	The server is either down for maintenance or you may have lost your connection.
	Unable to Locate the Server	The server indicated in the URL you typed or clicked from either no longer exists or was entered incorrectly.
	Viewer not Found	Your browser doesn’t recognise files of this type.
	You Can’t Log on as an Anonymous User	You must have a valid username and password to log onto this FTP site.