The HTTP response status code 301 Moved Permanently is used for permanent redirection. This status code should be used with the location header.
- If a client has link-editing capabilities, it should update all references to the Request URI. The response is cachable
- Unless the request method was HEAD, the entity should contain a small hypertext note with a hyperlink to the new URI(s).
- If the 301 status code is received in response to a request of any type other than GET or HEAD, the client must ask the user before redirecting.
More info in RFC 2616