IIS , Error. Access is Denied.

I have a Web home page which allows the IIS users account IUSR_Svr01 to view the Home page.

Each link on the Home page allows access to a sub folder containing further asp Web Pages, the access to the sub folder is restricted by the user having to provide the Domain, Account Name and Password in a dialog box.

My problem is that some users are presented with the access dialog box and provided the details are correct, they gain access, but other users are not presented with the dialog box and instead are presented with a page displaying;

Error. Access is Denied.

Directory Security is set to Anonymous Access and Integrated Windows Authentication.

Any help would be appreciated.

Maybe the failing users aren't using IE browser? Other browsers don't support NTLM authentication. There is supposedly some setting that will allow NTLM in Firefox but other browsers won't be able to authenticate unless you enable Basic authentication on the server.