This is not an easy question to answer, since he MAY have visited one or more of these sites. However, most likely he hasn't .
I keep getting the same e-mails over and over again from spammers, many saying women want to meet me and I've NEVER EVEN visited a dating website, much less entered my e-mail in one.
Spammers get e-mails from website you post on, like groups for hobbies and so. They also seem to be harvesting people's address books from computers they infect, presumably this also includes companies computers they get into.
I'm sorry, it would be reckless for me to say definitely whether he did or didn't visit one of these site, since no-one can really know for sure. All I can say is that if I found this sort of thing on my Wife's computer, I would not even consider it for a moment, unless there was something else as well that was making me suspicious.
I hope this helps a little? Good luck!