HTML Error Codes

Actually, they are better called response codes. Below is a list of the HTML error codes and its short description

Informational
100="Continue"
101="Switching Protocols"

Successful Client Requests
200 OK
201 Created
202 Accepted
203 Non-Authorative Information
204 No Content
205 Reset Content
206 Partial Content

Client Request Redirected
300 Multiple Choices
301 Moved Permanently
302 Moved Temporarily
303 See Other
304 Not Modified
305 Use Proxy

Client Request Errors
400 Bad Request
401 Authorization Required
402 Payment Required (not used yet)
403 Forbidden
404 Not Found
405 Method Not Allowed
406 Not Acceptable (encoding)
407 Proxy Authentication Required
408 Request Timed Out
409 Conflicting Request
410 Gone
411 Content Length Required
412 Precondition Failed
413 Request Entity Too Long
414 Request URI Too Long
415 Unsupported Media Type

Server Errors
500 Internal Server Error
501 Not Implemented
502 Bad Gateway
503 Service Unavailable
504 Gateway Timeout
505 HTTP Version Not Supported