In the briefest of terms, here it is: Blaise Pascal, a 17th Century French Mathematician, posited this argument in favour of his religion: If you're an atheist and you're right, then life is good enough for you, but there's no afterlife reward. If you're a christian and you're right, then life is good, and then you get a GREAT afterlife. If you're an atheist and you're wrong, then you will suffer horrible crap forever. If you're a christian and you're wrong, then no big deal, right? Therefore, the only good ending is in being a christian, the only bad ending is in being an atheist, and therefore everyone should join his religion.
It's a primitive argument, that's been refuted so many times in so many ways that when - as happened yesterday - I have some moron try to throw it at me, I can only laugh. Laugh and spend an hour or so working on a complex macro image so that from now on, I can just post a fucking link rather than waste time making the same arguments over and over again.
Also, I decided to have some fun with it, since I can no longer take this matter seriously.