Google has a strict list of content standards, and they don't accept AdSense on pages that are violating them. These include, among other things, sites that promote or sell:
- alcohol
- certain weapons
- firearms
- tobacco
- drugs
- designer knock-offs
This is a silly rule to violate, because AdSense is keyword generated, so it's amazingly easy for you to get caught. If you do have content that violates these rules, such as a beer-making supply store, they may be legitimate sites, but AdSense is not for you.