These are the standard status codes returned by a web server when we ask for a resource. Normally, when the server give us the resource we requested, we get a “200″ (OK) status code, even if the browser doesn’t show it because it shows the requested document instead.
When something goes wrong, we receive an error message, tipically “404″ (Page not Found), when the server can’t find the resource we asked at that specific location (path). This is probably the most common error you’ll come across. What has probably happened is that the web page you were going to has been removed or re-named.

100 : Continue
101 : Switching Protocols
200 : OK
201 : Created
202 : Accepted
203 : Non-Authoritative Information
204 : No Content
205 : Reset Content
206 : Partial Content
300 : Multiple Choices
301 : Moved Permanently
302 : Moved Temporarily
303 : See Other
304 : Not Modified
305 : Use Proxy
307 : Temporary Redirect
400 : Bad Request
401 : Unauthorized
402 : Payment Required
403 : Forbidden
404 : Not Found
405 : Method Not Allowed
406 : Not Acceptable
407 : Proxy Authentication Required
408 : Request Time-out
409 : Conflict
410 : Gone
411 : Length Required
412 : Precondition Failed
413 : Request Entity Too Large
414 : Request-URI Too Large
415 : Unsupported Media Type
416 : Requested range not satisfiable
417 : Expectation Failed
500 : Internal Server Error
501 : Not Implemented
502 : Bad Gateway
503 : Service Unavailable
504 : Gateway Time-out
505 : HTTP Version not supported