This charming type of ad automatically expands doubles and probably triples in size whenever you rollover them, which naturally ends up obscuring whatever you're trying to read!
I thought that desperately hunting for the well-hidden 'close' button while gunfire or revving engines ring in my ears was annoying enough, but these auto-expanding ones are just as bad, if not worse! The damn ads are strategically placed on the right hand side of the browser window, and extend nearly top to bottom, which practically ensures that you will constantly run over it as you use your mouse to scroll up and down the webpage. Alternatively, the ads run across the entire top edge of the webpage which is yet another area constantly crossed by one's mouse. Sometimes, they do both (top AND side ads) on the same webpage! And once they've expanded, they don't aways automatically shrink until you jiggle your mouse over them a few times. :P
The only way to avoid this is to take one's mouse on an absurdly circuituous detour to avoid the auto-expanding ad area(s) and/or to thread the narrow gaps between the ads.
And people call ME evil. ::sneer::