Need to block access to certain website types without listing each URL to block. Students at secondary school are going to porn sites. Need to be able to block all such access without having to list each possible site URL. Having the Content --> Ratings tab set to None for all categories on the ratings files listed on my computers does not prevent access.

Unchecking users may access sites with no rating, even with the security settings set to High, still allows the porn sites to come up. If that is checked, then ONLY listed sites can open and students would not be able to do any research via google, for example. I would rather not have to continue checking each computer and blocking sites as they find them.