These errors are commonly referred to as HTML error messages. But these messages are also called HTTP status messages. In fact, the server always returns a message for every request. The most common message is 200 OK.
| Notify | Describe |
| 200 OK | Request approved (this is the standard response for successful HTTP requests) |
| 201 Created | The request was made and a new resource was created |
| 202 Accepted | The request has been accepted for processing, but the processing is not complete yet |
| 203 Non-Authoritative Information | The request was processed successfully but is returning information possibly from another source |
| 204 No Content | The request was processed successfully but no content was returned |
| 205 Reset Content | The request was processed successfully, but did not return any content and requires the requesting party to reset the document view |
| 206 Partial Content | The server only distributes a portion of the resource by the scope header sent by the client |
| Notify | Describe |
| 400 Bad Request | The request could not be fulfilled due to incorrect syntax |
| 401 Unauthorized | The request is valid, but the server refuses to respond to it. Use when authentication is possible but fails or has not been specified |
| 402 Payment Required | Use for the future |
| 403 Forbidden | The request is valid, but the server refuses to respond to it |
| 404 Not Found | The requested page could not be found, but it may be available again in the future |
| 405 Method Not Allowed | The page was made using a request method that is not supported by the page |
| 406 Not Acceptable | The server can only generate a response that is not accepted by the client |
| 407 Proxy Authentication Required | The client must first authenticate itself using a proxy |
| 408 Request Timeout | The server has timed out waiting for the request |
| 409 Conflict | The request could not be completed due to a conflict in the request |
| 410 Gone | The requested page is no longer available |
| 411 Length Required | "Content-Length" is not defined. The server will not accept the request without it |
| 412 Precondition Failed | The precondition given in the request is evaluated as false by the server |
| 413 Request Too Large | The server won't accept the request because the request entity is too large |
| 414 Request-URI Too Long | The server won't accept the request because the URI is too long. Happens when you convert POST request to GET request with long query information |
| 415 Unsupported Media Type | The server will not accept the request, because the media type is not supported |
| 416 Range Not Satisfiable | The client requested part of the file, but the server could not provide that part |
| 417 Expectation Failed | The server could not respond to the requests of the Expect request-header . field |
| Notify | Describe |
| 500 Internal Server Error | Generic error message, given when no specific message matches |
| 501 Not Implemented | The server does not recognize the request method or is unable to make the request |
| 502 Bad Gateway | The server is acting as a gateway or proxy and received an invalid response from the upstream server |
| 503 Service Unavailable | Server is currently unavailable (overloaded or down) |
| 504 Gateway Timeout | The server is acting as a gateway or proxy and is not receiving a timely response from the upstream server |
| 505 HTTP Version Not Supported | The server does not support the HTTP protocol version used in the request |
| 511 Network Authentication Required | Client needs authentication to have network access |
