HTTP Error 401

Victor A. ( (no email) )
Thu, 30 Apr 1998 12:40:23 -0400

I've managed to figure all out regarding FTP etc, but now whenever any of
the users that I've setup using FTP tries to access their web site they
are asked for a user name and password ?!? and this error message:

HTTP Error 401
401.3 Unauthorized: Unauthorized due to ACL on resource

This error indicates that the credentials passed by the client do not have
access to the particular resource on the server. This resource could be
either the page or file listed in the address line of the client, or it
could be another file on the server that is needed to process the file
listed on the address line of the client.

Please make a note of the entire address you were trying to access and then
contact the Web server's administrator to verify that you have permission
to access the requested resource.

How does that happened? how do I fix it?