Status Codes
Responses from the server have a code indicating what happened.
HTTP server status codes are three-digit numbers and categorized, with each category using a range of 100 possible codes.
1xx Informational. * Request received, continuing response. Seldom used.
2xx Successful.
* 200 OK is the standard success response for a GET or POST.
* 201 Created request resulted in creation of a resource on the server.
* The server should return the URL representing the new resource in the Location: response header..
* 206 Partial Content client sent GET with a Range: request header, server provided just the requested range of content.
3xx Redirection. * Resource has moved, or has multiple versions, etc.; repeat request with the new URI provided in the response.
4xx Client Error.
* 404 Not found is common - client requested a nonexistent resource.
* 401 Unauthorized initiates an HTTP authentication exchange.
* 403 Forbidden might indicate a security violation.
5xx Server Error.
* 500 Internal Server Error usually indicates a problem with server-side code - a syntax error in a PHP or Perl script for example, or database error.
* 501 Not Implemented client sent an invalid request command.
* 503 Service Unavailable temporary server overload.
Resource: Status Code Definitions