When you visit a website your IP is usually logged, but the government never sees these logs, they are probably deleted weekly if not daily and even with logs they don't have the money, resources or right to subpeaona every internet service provider for your personal information.

Short answer: No, the government does not know you personally frequent drug related websites and no LEO isn't going to come knocking on your door for it. Just use common sense and don't post your full name, address, etc.