You can apply custom rules to allow traffic for specific sites and apps that are otherwise blocked by existing rules.
Custom rules override content rules. For example, if you use a content rule to block all sites in the "Video and photo" category, and a custom rule that allows http://www.pbskids.org, videos on pbskids.org will not be blocked. Similarly, if the content rule is set to allow the "Video and photo" category, but a custom rule blocks http://www.pbskids.org, all sites in the "Video and photo category" will be allowed, except pbskids.org.
The policy rules are applied to devices within the scope of the selected Organization Unit level.