HTTP Status and Error Codes Explained

1xx Informational
Request received, continuing process.
1. 100 Continue: The request has been completed and the rest of the process can continue.

2. 101 Switching: Protocols When requesting a page, a browser might receive a statis code of 101, followed by an "Upgrade" header showing that the server is changing to a different version of HTTP.


2xx Success
The action was successfully received, understood, and accepted.
1. 200 OK: Standard response for HTTP successful requests.
2. 201 Created: When new pages are created by posted form data or by a CGI process, this is confirmation that it worked.
3. 202 Accepted: The client's request was accepted, though not yet processed.
4. 203 Non-Authorative Information: The information contained in the entity header is not from the original site, but from a third party server.
5. 204 No Content: If you click a link which has no target URL, this response is elicited by the server. It's silent and doesn't warn the user about anything.
6. 205 Reset Content: This allows the server to reset any content returned by a CGI.
7. 206 Partial Content: The requested file wasn't downloaded entirely. This is returned when the user presses the stop button before a page is loaded, for example.

3xx Redirection
The client must take additional action to complete the request.
1. 300 Multiple Choices: The requested address refers to more than one file. Depending on how the server is configured, you get an error or a choice of which page you want.
2. 301 Moved Permanently: If the server is set up properly it will automatically redirect the reader to the new location of the file.
3. 302 Moved Temporarily: Page has been moved temporarily, and the new URL is available. You should be sent there by the server.
4. 303 See Other: This is a "see other" SRC. Data is somewhere else and the GET method is used to retrieve it.
5. 304 Not Modified: If the request header includes an 'if modified since' parameter, this code will be returned if the file has not changed since that date. Search engine robots may generate a lot of these.
6. 305 Use Proxy: The recipient is expected to repeat the request via the proxy.

4xx Client Error
The client failed to provide an valid request.
1. 400 Bad Request: There is a syntax error in the request, and it is denied.
2. 401 Authorization Required: The request header did not contain the necessary authentication codes, and the client is denied access.
3. 402 Payment Required: Payment is required. This code is not yet in operation.
4. 403 Forbidden: The client is not allowed to see a certain file. This is also returned at times when the server doesn't want any more visitors.
5. 404 Not Found: The requested file was not found on the server. Possibly because it was deleted, or never existed before. Often caused by misspellings of URLs.
6. 405 Method Not Allowed: The method you are using to access the file is not allowed.
7. 406 Not Acceptable: The requested file exists but cannot be used as the client system doesn't understand the format the file is configured for.
8. 407 Proxy Authentication Required: The request must be authorised before it can take place.
9. 408 Request Timed Out: The server took longer than its allowed time to process the request. Often caused by heavy net traffic.
10. 409 Conflicting Request: Too many concurrent requests for a single file.
11. 410 Gone: The file used to be in this position, but is there no longer.
12. 411 Content Length Required: The request is missing its Content-Length header.
13. 412 Precondition Failed: A certain configuration is required for this file to be delivered, but the client has not set this up.
14. 413 Request Entity Too Long: The requested file was too big to process.
15. 414 Request URI Too Long: The address you entered was overly long for the server.
16. 415 Unsupported Media Type: The filetype of the request is unsupported.

5xx Server Error
The server failed to fulfill an apparently valid request.
1. 500 Internal Server Error: Nasty response that is usually caused by a problem in your Perl code when a CGI program is run.
2. 501 Not Implemented: The request cannot be carried out by the server.
3. 502 Bad Gateway: The server you're trying to reach is sending back errors.
4. 503 Service Unavailable: The service or file that is being requested is not currently available.
5. 504 Gateway Timeout: The gateway has timed out. Like the 408 timeout error, but this one occurs at the gateway of the server.
6. 505 HTTP Version Not Supported: The HTTP protocol you are asking for is not supported.