Q: What are the common HTTP status codes?

1xx (Informational): The request has been received and is being processed.

100 Continue: The initial part of the request has been received, and the client should continue.
101 Switching Protocols: The server is switching to a different protocol as requested.

2xx (Success): The request was successfully received, understood, and accepted.

200 OK: The request was successful.
201 Created: The request succeeded, and a new resource was created.
202 Accepted: The request has been accepted but not yet processed.
204 No Content: The server successfully processed the request but is not returning any content.

3xx (Redirection): The client must take additional action to complete the request.

301 Moved Permanently: The requested resource has been permanently moved to a new URL.
302 Found: The requested resource has been temporarily moved to a different URL.
304 Not Modified: The resource has not been modified since the last request, and the client can use its cached version.

4xx (Client Error): The request contains bad syntax or cannot be fulfilled.

400 Bad Request: The server cannot process the request due to a client error.
401 Unauthorized: The request requires user authentication.
403 Forbidden: The server understood the request but refuses to authorise it.
404 Not Found: The server cannot find the requested resource.

5xx (Server Error): The server failed to fulfil a valid request.

500 Internal Server Error: The server encountered an unexpected condition.
503 Service Unavailable: The server is currently unable to handle the request, usually due to being overloaded or down for maintenance.