HTTP Response Header Status description

The status code consists of three digits, the first number defines the category of the response, and there are five possible values:
1XX: Indication information--Indicates that the request has been received and continues processing
2XX: Success-Indicates that the request has been successfully received, understood, accepted
3XX: Redirect--further action is required to complete the request
4XX: Client Error--Request syntax error or request not implemented
5XX: Server-side error-the server failed to implement a legitimate request
Common status codes, status descriptions, descriptions:
$ OK//client request succeeded
Bad Request//client requests have syntax errors and cannot be understood by the server
401 Unauthorized//request unauthorized, this status code must be used with the Www-authenticate header field
403 Forbidden//server receives request, but refuses to provide service
404 Not Found//request resource not present, eg: Wrong URL entered
Internal Server error//server unexpected errors
503 Server Unavailable//server is currently unable to process client requests and may return to normal after some time

HTTP Response Header Status description