To listen for Web Proxy client requests
In the console tree of ISA Server Management, click Networks.
In the details pane, click the Networks tab, and then select the applicable network.
On the Tasks tab, click Edit Selected Network.
On the Web Proxy tab, select Enable Web Proxy client connections for this network.
To open ISA Server Management, click Start, point to All Programs, point to Microsoft ISA Server, and then click ISA Server Management.
For ISA Server 2006 Enterprise Edition, expand Microsoft Internet Security and Acceleration Server 2006, expand Arrays, expand Array_Name, expand Configuration and then click Networks.
For ISA Server 2006 Standard Edition, expand Microsoft Internet Security and Acceleration Server 2006, expand Server_Name, expand Configuration and then click Networks.
Web Proxy client properties cannot be configured for the following built-in networks: External, Quarantined VPN Clients, and VPN Clients.
To enable listening for HTTP requests, select Enable HTTP. To enable listening for Secure Sockets Layer (SSL) requests, select Enable SSL. The SSL option exists primarily for requests from a downstream Web Proxy that sends requests to ISA Server over SSL. For this option, you must have a server authentication certificate installed on ISA Server. For more information about certificates, see "Digital Certificates for ISA Server" at the (http://www.microsoft.com/).