Porn websites generate a lot of traffic, which means you need some pretty solid technical skills and good decision making abilities in order to get something like that up and running and keeping it that way. On top of this, such sites tend to scale relatively fast, you have to be ready for it.
Also, most of the good techniques used to monetize a website also apply to such a site, and this is not as easy as it sounds.
Now on with your question: it's good that you have these concerns, it shows that you are concious about the potential problems that can arise from you or your employer being associated with such a product.
I would put it on my resume, but ONLY if it was a project for a client, not something I worked on completely on my own. Also, I would leave out anything about the site's name or its type of content. Instead I would say something like:
I worked on a big and popular project that served high volumes of
media. I implemented it in technology X, Y and Z. Reduced operating
costs by using techniques A, B and C. My expertise and advice allowed
it to grow in popularity, generating $300K profit for the client every
The whole idea is that you prove your technical skills (which is what the interview is all about) without damaging your image.
When asked for a link to the website or more details about it, tell them that it's a porn site but put very very strong emphasis on the fact that:
- you did this for a client
- you are no longer associated with that project in any way (I'm assuming this is the case)
- the fact that you worked on this is not public knowledge, so your presence in the company will not damage its image (this last point is CRUCIAL)
If you feel you can safely pull this off, then go ahead. Otherwise, if you have a dozen other projects you worked on, I wouldn't bother; those other projects will probably be enough to demonstrate your skills.
A final point I want to make: if you leave it out of your resume, your interviewer(s) might ask what you did in that 6-month gap of your work history. You could tell them you spent that time learning new technologies and improving your skills. This is technically not a lie and it's a good answer in this situation.