NOT MODIFIED 304
If the client has done a conditional GET and access is allowed, but
the document has not been modified since the date and time specified
in If-Modified-Since field, server responds with 304 status code, and
does not send the document back to the client.
NEW: Response headers are as if the client had originally sent a HEAD request.
NEW: This way the server can upload a new expiry date and other necessary
NEW: metainformation to the requesting client (often a caching proxy).
This is to allow fast update of caches.
-- Cheers, Ari --