Lame_Wolf - 10:11 pm on Mar 11, 2012 (gmt 0)
Neither of those, Ken_b
I am talking about adsense, not serps.
Think of a 336 x280 ad unit.
Instead of getting 4 adverts, I see 3 adverts and 3 (sometimes 4) link units where the last advert should be.
Same thing for a wide skyscraper:
Only happens with old code and IE6 (no idea of later versions).