List of HTTP Status Code

1xx

100 (continue)
101 (Switching Protocols)

2xx

200 (OK)
201 (Created): respond to POST Request in RESTFul.
202 (Accepted): Server fetch the request, but not respond immediately.
203 (Non-Authoritative Information).
204 (No Content): Server has handled the request, but no content need to be respond.
205 (Reset Content): Server has handled the request, and no content need to be respond. But server request client to reset the document(recover to that before submission).
206 (Partial Content): HTTP allowed transferring by piece of data.

3xx

3xx request more operation from client, usually redirect to other page.

Destination redirect to will be specified in Location in header.

301 (Moved Permanently): The resource has been moved to new position.
302 (Found): The resource will be returned from other url temporarily.
303 (See Other)
304 (Not Modified): Usually work with Etag

Server will return 304 with Etag: '***' to specify resource version. Next time the client request the resource with If-None-Match: '***', and server checks if the Etag is same to If-None-Match. If same, then return 304.

4xx

Client Error.

400 (Bad Request)
401 (Unauthorized): Server responds with WWW-Authenticate for authorization info, and client should request with authorization in header next time.
403 (Forbidden): Server got the request, and refuse to handle.
404 (Method Not Allowed)
413 (Request Entity Too Large)
414 (Request-URI Too Large)