The biggest virus going around right now gets downloaded from a pop-up that says "Windows Security" and is very nasty and convincing. I've gotten the pop up a couple of times myself, which is funny because I use a Mac. Anyways, so long as you don't click it at all, you should be alright.
When you do get it, it might not let you close your browser so be sure to Cntrl+Alt+Delete to go a user screen, click "Task Manager", and force quit your internet browser. If you're using a Mac, click the Apple icon in the upper left corner, click "Force Quit", and click the browser.
If anyone has any better suggestions, probably a good idea to start a new thread ^^;
That awkward moment where you're trying to be helpful and get off-topic.