Just so we're reading from the same page,pop ads arethose things that open in new windows,and each is the size of three monitors set to a resolution of 10 by 10 pixels,and each time you close one 2 raised to N others open.
What yahoo has had are reasonably sized ads embedded on the page,and these ads don't obstruct from what you're doing,infact sometimes yuo have to scroll to see the ad in full.
And out of curiosity,what email service doyou use?