"The ISA Server denies the specified Uniform Resource Locator (URL)" error message when a client tries to connect to the Internet through ISA Server 2006, ISA Server 2004, or Microsoft Forefront Threat Management Gateway, Medium Business Edition

After you install Microsoft Internet Security and Acceleration (ISA) Server 2006, ISA Server 2004, or Microsoft Forefront Threat Management Gateway, Medium Business Edition, when a client browser tries to connect to aWeb address, the client may receive one of the following error messages:

This behavior occurs because the firewall does not permit any traffic after the initial installation of ISA Server is complete. By default, when you install ISA Server or Microsoft Forefront Threat Management Gateway, Medium Business Edition, a default rule is created that denies all access to and from all networks. This default rule cannot be modified or deleted. The default rule is always processed last.

To resolve this behavior, you must set up firewall policy rules that permit traffic. To do so, follow these steps:

1. Click Start, point to Programs, point to Microsoft ISA Server, and then click ISA Server Management.
2. In the left pane, click ServerName, where ServerName is the name of your ISA Server computer.
3. In the middle pane, under Getting Started, click View and Create Firewall Policy Rules.
4. In the right pane, click the Tasks tab.
5. Click Create New Access Rule.
   
   Note In ISA Server 2006 or in Microsoft Forefront Threat Management Gateway, Medium Business Edition, click Create Access Rule.
6. Follow the steps in the New Access Rule Wizard to create an access rule that permits the traffic that you specify.

This behavior is by design.