This site is weird. Thankfully, it started as a joke. CheatNeutral is a criticism of carbon offsetting companies. If you click the "About" link at the top of the page, then you can read about carbon offsetting.
It's pretty easy to look at and wonder how CheatNeutral could work. The answer is that it doesn't work. I mean, I'm pretty sure nobody actually pays them and they don't pay people. But I didn't sign up as a sinle/monogamous person so I don't actually know. Furthermore, you'd never show your partner the offset certificate. Also, 2 and a half pounds is an absurdly small price to pay for cheating. Browse around the site, though.
Cheating on me has thankfully never happened before (to the best of my knowledge) and it is the one thing that would make me terminate a relationship instantly. No sort of offsetting payment could be made directly to me, let alone to a third (or, better, 4th) party.