When an end user tries to access a Web Site or other content that is blocked by the Web Gateway, they do not get a notification page and the connection times out.
This is normally a routing issue. The Web Gateway and the client are not able to talk with each.
1. Verify that a static route for the clients network is on the Administration - Configuration - Network Page.
2. This can also be caused by other network devices responding to ARP request for IP address other than there own. One example is ARP Proxy that is available on some firewalls.
Symantec Web Gateway in inline or inline proxy modes.