Internet works fine, but...

Hello,
I just received my new computer today in the mail. And I was excited and all, yes, like any other boy would be. Anyway, back to the point. I was browsing around on the internet, minding my own business. And all of the sudden, Firefox says it couldn't pick up any connection. Which is odd. But my brothers computer, which is right next to me, doesn't seem to be experiencing the same problem. Infact, the loss of connection just happens on browsers. I still stay connected on Warcraft and junk like that. Excuse me if this is a newb question, I don't have much experience when it comes to stuff like this.