There is the "adult content" category for sexually implicit content, but it would be great to have also a category that includes non-sexual content that could be harmful for kids below 18 and also should not be accessible from a work device for obvious reasons.
I am thinking of content with glorification of violence and crime, tasteless, often gory photographs, such as autopsy photos, photos of crime scenes, crime and accident victims, excessive obscene material, shock websites etc.