Response codes

200 - OK
206 - Partial Content (if successfully returned part of the file)

301 - Moved permanently 
302 - Found (temporary redirect)
303 - See other
304 - Not Modified

400 - Bad Request
401 - Not Authorized
403 - Forbidden
404 - Not Found
405 - Method Not Allowed
406 - Not Acceptable

Basic and Digest authentication

Covered by rfc 2617

Basic adds Authorization: header, e.g.: Authorization: Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ== where the value after Basic is base64 encoding of string ${userid} “:” ${password}

Digest is more complicated. Server responds with e.g.:

HTTP/1.1 401 Unauthorized
WWW-Authenticate: Digest
   realm="testrealm@host.com",
   qop="auth,auth-int",
   nonce="dcd98b7102dd2f0e8b11d0f600bfb0c093",
   opaque="5ccc069c403ebaf9f0171e9517f40e41"

And client has to reply with:

Authorization: Digest username="Mufasa",
   realm="testrealm@host.com",
   nonce="dcd98b7102dd2f0e8b11d0f600bfb0c093",
   uri="/dir/index.html",
   qop=auth,
   nc=00000001,
   cnonce="0a4f113b",
   response="6629fae49393a05397450978507c4ef1",
   opaque="5ccc069c403ebaf9f0171e9517f40e41"