Chapter 15 Unified Threat Management for FortiOS 5.0 : Web filter : Working with the Interface : URL Filter
  
URL Filter
Allow or block access to specific URLs by adding them to the URL filter list. Add patterns using text and regular expressions (or wildcard characters) to allow or block URLs. The unit allows or blocks web pages matching any specified URLs or patterns and displays a replacement message.
You can add multiple URL filter lists and then select the best URL filter list for each profile.
You can add the following to block or exempt URLs:
complete URLs
IP addresses
partial URLs to allow or block all sub-domains
Each URL filter list can have up to 5000 entries.