Status code groups from web servers

Web servers give to browser responses in different areas of digits. It not needed for me as for developer to memorize all response codes, but it was needed in one project to know what response means. I found some useful information and I'd like to share it (in the Self training Kit)

Status code group	Description
1xx	Informational: received request, continue process
2xx	Action was received, understood and accepted
3xx	This is redirect command. Further action must be taken to complete the request.
4xx	Everybody knows that this is error codes :) like page is not available, etc...
5xx	This means that web server has some problems