1.201-206 all indicate that the request is successful
200 - success
201-created
202 - Accepted: The server accepted the request but did not process it
203 - Unauthorized Information
204 - no content
205 - reset content
206 - Partial content
2.300-307 indicates that further operations are required to complete the request, and the code status is usually redirection (300 I don't see much)
3.400-417 indicates that the request may have gone wrong, preventing the server from processing
400 - Request syntax not understood by server
401 - Authentication Error
403 - The server rejected the request
404 - Page Not Found (most common server status)
405 - Method Disabled
406 - Not Accepted (Cannot respond to the requested web page with the requested content attribute)
407 - Proxy authorization required
408 - request timed out (the server timed out waiting for the request)
409 - Conflict
410 - Deleted
411 - valid-length required (server does not accept requests without a valid-length header field)
412 - Precondition not met
413 - Request entity too large
414 - The requested URL is too long
415 - Unsupported media type
416 - The requested range does not meet the requirements
417 - To meet expectations
4.500-505 means: The server has an internal error while trying to process the request, it's the server's fault, not the request's fault
500 - Internal server error (for example, the server of the test environment hangs)
501 - The server is not capable of fulfilling the request
502-Error network management
503 - Server unavailable (overloaded or down for maintenance, paused state)
504 - Gateway Timeout
505 - http version not supported (request using http protocol version not supported by server)