Answers:
Check here for more details
http://www.networksorcery.com/enp/protoc...
4xx: Client error.
The request contains impossible syntax or cannot be fulfilled at this server.
406 - Not reasonable.
486 - Busy here.
:)
Go to Google, type in your press as it is above. It will bring you to this net site.
http://scholar.google.com/scholar?q=diff...