If you are showing ads on the Display network, you can exclude entire categories of websites and pages, which discuss potentially sensitive topics from showing your ads. Your display traffic will be more efficiently targeted and you'll prevent your ads from appearing on questionable pages.
The category exclusions that are most pressing to exclude are:
Crime, police & emergency
Death & tragedy
Military & International Conflict
Juvenile, gross & bizarre content
Profanity & rough language
Sexually suggestive content
You may also want to consider excluding the following:
Error pages
Parked domains
Review ad performance on Error pages and Parked domains before you decide to exclude them.