Safari and Google Chrome running slow on my MacBook

Hi there!

Over the last couple of weeks Safari (and Google Chrome) have started running very, very slow on my MacBook(I own a MacBook white, OS X version 10.6.8). I didn't install anything new over the last few months, so I don't think that is the problem. My Wi-Fi has been checked and that's not the problem either. Also, I emptied my cache and reset Safari, yet nothing seems to help.. Sometimes I even have to Force Quit Safari because it just stops working all of a sudden and it blocks my whole computer for over a minute. Anyone out there that can help me?