401 error – sub status code list

    401.1:  Access is denied due to invalid credentials.
    401.2:  Access is denied due to server configuration favoring an alternate authentication method.
    401.3:  Access is denied due to an ACL set on the requested resource.
    401.4:  Authorization failed by a filter installed on the Web server.
    401.5:  Authorization failed by an ISAPI/CGI application.
    401.7:  Access denied by URL authorization policy on the Web server.