Most common HTTP status codes

200 (OK): The resource was found and all is well.

304 (NOT MODIFIED): The resource has not been modified since the last request. This is used most often for browser cache mechanisms.

401 (UNAUTHORIZED) : The clien is not authorized to handle the resource. Often, this will cause the browser to ask for a username and password to log in to the server.

403 (FORBIDDEN): The client failed to gain authorization. This typically happens if you fail to log in with the correct username and password after a 401.

404 (NOT FOUND): The resource does not exist at the given location.