Can an iPhone 3Gs get infected from a pop up?

[Claire]

I was searching for world flags and a stupid pop up came on saying that I had been selected to win something. So, I shut down my phone to see if it'd just go away, but it didn't. I couldn't close the window either, so I had no choice but to click "ok". I then quit out of safari, shut down my phone, powered it back up, and am asking this question now. So, is it possible for my iPhone to have a virus now? :-/