The user is prompted for credentials when trying to access the internal Web site.
Cause: The internal Web site is based on Windows SharePoint Services. To use this site, users must be members of a Windows SharePoint Services site group. A user who is prompted for credentials does not have a site group membership.
Solution: Create user accounts based on Windows Small Business Server templates. User accounts based on these templates have permission to access the internal Web site because the templates are members of the site groups by default.
For more information, open Help and Support, and search for the topic "To add a user account."