Every HTTP status code with its meaning and when to use it, from 100 Continue to 511.
Status codes are grouped by class: 1xx informational, 2xx success, 3xx redirection, 4xx client error, 5xx server error. The class alone tells a caller whether retrying could possibly help.
When should I use 401 instead of 403? 401 means you have not authenticated, so credentials might help. 403 means you are authenticated but not allowed, so they will not.
Is 301 or 302 right for a redirect? Use 301 when the move is permanent and you want search engines to transfer ranking. Use 302 for anything temporary.