Can you get AIDS any type of STD from using a public bathroom? Like if anybody masturbated and left semen on a toilet seat, and your genitals touched the toilet seat?

Transmission of the virus needs to be introducted directly into body via cuts, or touched and placed into your mouth, eyes, nose etc.

You can't get HIV just by sitting on the toilet seat.

Unless you sit on a dirty one, with an open wound. Mind you there would have to be some one's bodily fluids on there who had the virus to start with. May want to wait 3 months before having sex, and get tested to be sure though. You never know, right.

It's highly unlikely, as the AIDS virus dies within 20 seconds of being airborne.

We never know, but personally I wouldn't worry about it.