The administrator created a URL filtering rule to block web sites included in the adult category. However, a particular adult site was allowed despite the fact that it was displayed in the transaction report and rated as ADULT.
The reason for this is that this URL actually belonged to more than one category: ADULT_THEMES and DISCUSSION_FORUMS and ON-LINE_CHAT. In this case, there was a URL filter rule that allowed ON-LINE_CHAT for the end user, and this rule was running before the rule blocking Adult sites.
In this case, you need to change the order of the URL rules, setting the ADULT_THEMES rule before any other rules.