You have to be careful with this stuff. There are a few things to consider.
It is now a law (Federal law 18 USC 2257) that you keep records of all models portrayed in a sexual way proving at the time of photography they where over 18 years old.
You also have to make some sort of an effort so children will not be exposed to the material. Yes it is impossible to stop children typing a wrong year in to bypass you age detection system, but in a court it will look better if you have tried.
In general you should be fine. Porn is a subject not many people want to take to court (unless it is harming minors or rape, etc) over minor things because it's seen as dirty and more people who see it who don't want will just leave and never mention it again.
But there are always the one offs. Just cover you back and put a warning page on the entrance. Also submit your website to adult censors such as Bernardo's (I think it is) dreaming your site as inappropriate for children.
Read up on adult webmasters sites and google. So long as you can prove the models are not copyrighted images (affliate will be okay) and over 18 you're fine.
Oh wait, one other thing, make sure it's legal to publish porn in your state/country
Mark