If you log on to a Windows 2000-based ISA Server as an unauthenticated user, and start Internet Explorer, you receive:
401 Unauthorized - The server requires authorization to fulfill the request.
Access to the Web server is denied. Contact the server administrator.
This behavior will occur if the server is NOT configured to permit unauthenticated users.
To permit unauthenticated users:
1. In the console tree of ISA Management, right-click the server, or array node, and press Properties.
2. Select the Incoming Web Requests tab.
3. Clear the Ask unauthenticated users for identification check box.
4. Press OK.