Google AdSense publishers aren’t allowed to place Google ads on web pages that contain adult content but what exactly constitutes adult content in the eyes of Google?
google adults

Make sure your web pages are family-safe
Cecelia Choi from the AdSense Policy team offers a simple rule of thumb to help you quickly decide whether a picture or piece of text falls in the adult category or not:
If you wouldn’t want a child to see the content or if you would be embarrassed to view the page in front of colleagues, then it’s probably not family-safe and you shouldn’t place AdSense ad code on it.
One more thing. The AdSense rules also prohibit ads on web pages that either link to external sites that have mature content or if you have other advertisers who could be serving adult ads on your pages.
I have seen several AdSense publishers using “traffic widgets” from services like MGID or 2Leep – you don’t have enough control on what kind of pictures are getting served through these widgets and thus they could pose a risk to your AdSense account.