HTTP Error Codes and what they mean :

Web servers will use the following Error Codes when something goes awry. Knowing what they mean enables you to fix the problem, or create custom error pages.

The status codes are returned to the client making the request (typically an Internet Browser) and also recorded in the server's log file. Theses error codes are encoded into decimal ranges:
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Error Code RangeType of Error Code
100 to 199 Informational status codes, rarely used - and generally only written to server logs.
200 to 299 Successful, only 200 frequently used - and generally only written to server logs.
300 to 399 Warning - but the request may still be satisfiable.
400 to 499 Client Error, the request was invalid in some way.
500 to 599 Server Error, the server could not fulfil the (valid) request.

HTTP Error
Description
100 Continue. Not really an "error", this HTTP Status Code means everything is working fine.
101 Switching Protocols. Again, not really an "error", this HTTP Status Code means everything is working fine.
200 Success. This HTTP Status Code means everything is working fine. However, if you receive this message on screen, obviously something is not right... Please contact the server's administrator if this problem persists. Typically, this status code (as well as most other 200 Range codes) will only be written to your server logs.
201 Created. A new resource has been created successfully on the server.
202 Accepted. Request accepted but not completed yet, it will continue asynchronously.
203 Non-Authoritative Information. Request probably completed successfully but can't tell from original server.
204 No Content. The requested completed successfully but the resource requested is empty (has zero length).
205 Reset Content. The requested completed successfully but the client should clear down any cached information as it may now be invalid.
206 Partial Content. The request was canceled before it could be fulfilled. Typically the user gave up waiting for data and went to another page. Some download accelerator programs produce this error as they submit multiple requests to download a file at the same time.
300 Multiple Choices. The request is ambiguous and needs clarification as to which resource was requested.
301 Moved Permanently. The resource has permanently moved elsewhere, the response indicates where it has gone to.
302 Moved Temporarily. The resource has temporarily moved elsewhere, the response indicates where it is at present.
303 See Other/Redirect. A preferred alternative source should be used at present.
304 Not Modified. The server has identified from the request information that the client's copy of the information is up-to-date and the requested information does not need to be sent again.
305 Use Proxy. The request must be sent through the indicated proxy server.
307 Temporary Redirect The resource has temporarily moved elsewhere, the response indicates where it is at present. Client should still use this URL.
400 Bad Request. Due to malformed syntax, the request could not be understood by the server. The client should not repeat the request without modifications. Please contact the server's administrator if this problem persists.
401.1 Unauthorized: Logon Failed. This error indicates that the credentials passed to the server do not match the credentials required to log on to the server. Please contact the Web server's administrator to verify that you have permission to access the requested resource.
401.2 Unauthorized: Logon Failed due to server configuration. This error indicates that the credentials passed to the server do not match the credentials required to log on to the server. This is usually caused by not sending the proper WWW-Authenticate header field. Please contact the Web server's administrator to verify that you have permission to access to requested resource.
401.3 Unauthorized: Unauthorized due to ACL on resource. This error indicates that the credentials passed by the client do not have access to the particular resource on the server. This resource could be either the page or file listed in the address line of the client, or it could be another file on the server that is needed to process the file listed on the address line of the client. Please make a note of the entire address you were trying to access and then contact the Web server's administrator to verify that you have permission to access the requested resource.
401.4 Unauthorized: Authorization failed by filter. This error indicates that the Web server has a filter program installed to verify users connecting to the server. The authentication used to connect to the server was denied access by this filter program. Please make a note of the entire address you were trying to access and then contact the Web server's administrator to verify that you have permission to access the requested resource.
401.5 Unauthorized: Authorization failed by ISAPI/CGIapp. This error indicates that the address on the Web server you attempted to use has an ISAPI or CGI program installed that verifies user credentials before proceeding. The authentication used to connect to the server was denied access by this program. Please make a note of the entire address you were trying to access and then contact the Web server's administrator to verify that you have permission to access the requested resource.
403.1 Forbidden: Execute Access Forbidden. This error can be caused if you try to execute a CGI, ISAPI, or other executable program from a directory that does not allow programs to be executed. Please contact the Web server's administrator if the problem persists.
403.2 Forbidden: Read Access Forbidden. This error can be caused if there is no default page available and directory browsing has not been enabled for the directory, or if you are trying to display an HTML page that resides in a directory marked for Execute or Script permissions only. Please contact the Web server's administrator if the problem persists.
403.3 Forbidden: Write Access Forbidden. This error can be caused if you attempt to upload to, or modify a file in, a directory that does not allow Write access. Please contact the Web server's administrator if the problem persists.
403.4 Forbidden: SSL required. This error indicates that the page you are trying to access is secured with Secure Sockets Layer (SSL). In order to view it, you need to enable SSL by typing "HTTPs://" at the beginning of the address you are attempting to reach. Please contact the Web server's administrator if the problem persists.
403.5 Forbidden: SSL 128 required. This error message indicates that the resource you are trying to access is secured with a 128-bit version of Secure Sockets Layer (SSL). In order to view this resource, you need a browser that supports this level of SSL. Please confirm that your browser supports 128-bit SSL security. If it does, then contact the Web server's administrator and report the problem.
403.6 Forbidden: IP address rejected. This error is caused when the server has a list of IP addresses that are not allowed to access the site, and the IP address you are using is in this list. Please contact the Web server's administrator if the problem persists.
403.7 Forbidden: Client certificate required. This error occurs when the resource you are attempting to access requires your browser to have a client Secure Sockets Layer (SSL) certificate that the server recognizes. This is used for authenticating you as a valid user of the resource. Please contact the Web server's administrator to obtain a valid client certificate.
403.8 Forbidden: Site access denied. This error can be caused if the Web server is not servicing requests, or if you do not have permission to connect to the site. Please contact the Web server's administrator.
403.9 Access Forbidden: Too many users are connected. This error can be caused if the Web server is busy and cannot process your request due to heavy traffic. Please try to connect again later. Please contact the Web server's administrator if the problem persists.
403.10 Access Forbidden: Invalid Configuration. There is a configuration problem on the Web server at this time. Please contact the Web server's administrator if the problem persists.
403.11 Access Forbidden: Password Change. This error can be caused if the user has entered the wrong password during authentication. Please refresh the page and try again. Please contact the Web server's administrator if the problem persists.
403.12 Access Forbidden: Mapper Denied Access. Your client certificate map has been denied access to this Web site. Please contact the site administrator to establish client certificate permissions. You can also change your client certificate and retry, if appropriate.
403.13 Client certificate revoked: The page you are trying to view requires the use of a valid client certificate. Your client certificate was revoked, or the revocation status could not be determined. The certificate is used for authenticating you as a valid user of the resource.
403.14 Directory listing denied: This Virtual Directory does not allow contents to be listed.
403.15 Client Access Licenses exceeded: There are too many people accessing the Web site at this time.
403.16 Client certificate untrusted or invalid: The page you are trying to view requires the use of a valid client certificate. Your client certificate is untrusted or invalid. The client certificate is used for authenticating you as a valid user of the resource.
403.17 Client certificate has expired or is not yet valid: The page you are trying to view requires the use of a valid client certificate. Your client certificate has expired or is not yet valid. The client certificate is used for identifying you as a valid user of the resource.
404 Not Found: The Web server cannot find the file or script you asked for. Please check the URL to ensure that the path is correct. Please contact the server's administrator if this problem persists.
404.1 Web site not found. (You can probably change the wording to read "Web site" instead of "Web server". The Web site you are looking for is unavailable due to its identification configuration settings.)
405 Method Not Allowed: The method specified in the Request Line is not allowed for the resource identified by the request. Please ensure that you have the proper MIME type set up for the resource you are requesting. Please contact the server's administrator if this problem persists.
406 Not Acceptable: The resource identified by the request can only generate response entities that have content characteristics that are "not acceptable" according to the Accept headers sent in the request. Please contact the server's administrator if this problem persists.
407 Proxy Authentication Required: You must authenticate with a proxy server before this request can be serviced. Please log on to your proxy server, and then try again. Please contact the Web server's administrator if this problem persists.
408 Request Time-Out. The client did not send a request within the required time period.
409 Conflict. There is an internal conflict of access to the resource. Please contact the server's administrator if this problem persists.
410 Gone. The requested resource used to be on the server but is no longer available. Any robot seeing this response should delete the reference from its information store.
411 Length Required. The request requires the Content-Length HTTP request field to be specified.
412 Precondition Failed: The precondition given in one or more of the Request-header fields evaluated to FALSE when it was tested on the server. The client placed preconditions on the current resource meta-information (header field data) to prevent the requested method from being applied to a resource other than the one intended. Please contact the Web server's administrator if the problem persists.
413 Request Entity Too Large. The URL is too long (possibly too many query strings?).
414 Request-URI Too Long: The server is refusing to service the request because the Request-URI is too long. This rare condition is likely to occur only in the following situations:
  • A client has improperly converted a POST request to a GET request with long query information.
  • A client has encountered a redirection problem (for example, a redirected URL prefix that points to a suffix of itself).
  • The server is under attack by a client attempting to exploit security holes present in some servers using fixed-length buffers for reading or manipulating the Request-URI.
Please contact the Web server's administrator if this problem persists.
415 Unsupported Media Type. The server does not support the resource type requested. Frequently found when attempting to serve up content which may require a plug-in. See also: Mime Types
416 Requested Range Not Satisfiable. The portion of the resource requested is not available or out of range.
417 Expectation Failed. The Expect specifier in the HTTP request header can not be met.
500 Internal Server Error: The Web server is incapable of performing the request. Please try your request again later. Please contact the Web server's administrator if this problem persists.
500.12 Application restarting: There is a problem with the page you are trying to reach and it cannot be displayed.
500.13 Server too busy: There is a problem with the page you are trying to reach and it cannot be displayed.
500.15 Requests for Global.asa not allowed: There is a problem with the page you are trying to reach and it cannot be displayed.
500-100.asp ASP error: There is a problem with the page you are trying to reach and it cannot be displayed.
501 Not Implemented: The Web server does not support the functionality required to fulfill the request. Please check your URL for errors, and contact the Web server's administrator if the problem persists.
502 Bad Gateway: The server, while acting as a gateway or proxy, received an invalid response from the upstream server it accessed in attempting to fulfill the request. Please contact the Web server's administrator if the problem persists.
503 Out of Resources. Service temporarily unavailable - typically because it is currently overloaded.
504 Gateway Time-Out: Unable to connect to origin web server. The web site you are attempting to access is currently unreachable. This may be due to a network outage, or the web site might be experiencing technical difficulties.
505 HTTP Version not supported. The request uses a version of HTTP that is not supported.

The Final Word
:
The Internet HTTP1.1 protocol specifies the entire set of errors that are recorded by most servers. Please refer to RFC2616 for the authoritative explanation.