You have a requirement to block access to all sites of a specific category except for one specific site, for example, block all Social Networking sites except Facebook or all Audio/Video sites except YouTube. However, doing this produces an incomplete web page for that required site, for example, all images are missing or the formatting is incorrect.
In a new or existing Web Access Layer, create the following rules:
Now, when someone goes to the Facebook site they will be allowed access. When the browser tries to load the images that exist on the subsidiary sites, the proxy will also allow them as it will know that they are being requested by the Facebook site.