Dr. Tom Shinder has published a new article on using the new Web Access Policy node.  Tom says:

This new node provides a location where you can configure the TMG firewall to allow outbound HTTP, HTTPS and Web proxy forwarded FTP connections to the Internet. This change also seems to represent an increased focus on HTTP for the product. While previous versions of the ISA Firewall did have a sophisticated Web proxy filter and HTTP Security Filter, the TMG firewall takes things to the next level by adding malware inspection for outbound HTTP requests.

Read the rest of the article at the source.

Source: Creating a Web Access Policy using the Forefront Threat Management Gateway (TMG) Beta 1 (Part 1)