Jenstar - 7:30 pm on Nov 26, 2003 (gmt 0)
It could also possibly be the difference between the? or the =, or when there is a combination of the two. When Google made the switch, it would spider the?keyword and show the targeted ads to the page, not the content. I haven't checked since then, though - they could have flagged all?keyword, even if the keyword isn't a true keyword but something used legitimately for tracking purposes. It could show PSAs because it is something many were using for scammy reasons, but which could have caught many honest publishers in the crossfire.