Here are the most common codes and messages you’re likely to see on your Web browser (HTTP), when accessing Usenet, using e-mail, or using the FTP protocol to upload or download files.
The codes can generally by grouped as follows –
100-199 – Information Codes. Provide information about the request or the servers involved.
200-299 – Success Codes. Indicate that the request was accepted or the requested file has no content (empty).
300-399 – Redirects. Requested content has moved.
400-499 – Client Errors. Cannot find content or you don’t have the correct permissions to access it.
500-599 – Server Errors. There is a problem at the server end stopping the request from completing successfully.