How to stop unwanted ads popping in new windows?

I use Firefox 3.6 in this computer and I clicked on pop-up blocker even set my internet options to block all cookies and turned on pop-up blocker and even tried the block-ads addoon in firefox but still, when I open one site there's always an ad that pop-ups in a new window I even copied the site and blocked it and it still pop-up. I checked my installed programs to see if there's anyt programs that were installed without my permission and so far there was nothing out of ordinary but please help me how to stop the ads from opening a new window! Thanks.. btw, I use Norton 360 V.4

Hi

 

 

You might have a n aware problem

 

 

to confirm if you have any threat or not you could give malware bytes a try

 

here`s the link   http://download.cnet.com/Malwarebytes-Anti-Malware/3000-8022_4-10804572.html