Adblock Plus is an open source advertisement and tracking blocker that prevents certain pop-up ads and stop cookies from tracking your online activity.
Adblock Plus only blocks what you instruct it to block via filter lists which can also be configured to block malware as well. Adblock Plus strives to permit legitimate "Acceptable ads" and block more malicious or aggressive pop-up ads.
However, if you want it to block absolutely everything ad related, you can.
Download AdBlock Plus for Safari 1.7.2.1099 Beta in