You Are not Authorized Problem

[aalva]

I have internet authentication for all my users , so qhen they need to enter to internet they have to enter his/her username and password, everything is ok.
But when i need to enter this page

http://www.advancedintl.com/asp/

the first thing that appears is a page that said that your are not authorized. If i used some other method to enter internet it supposed to appear when i enter this page a combo box asking me a user and a password. It seems that this page take the user and password authentication of Internet as user and password for that page.

Im using Proxy server 2.0 and i cant use ms client because i have a Novell network. Pls Some Help