Let me quote some rather startling numbers to you from a recent eye tracking study we did. In the study, we looked at where people first looked on a search results page, where they first scanned a listing, and where they eventually clicked.
First of all, we gave participants a number of different scenarios that involved looking to a search engine to help them make a purchase. We used Google, Yahoo and MSN in the study. In all cases, on all 3 engines, the vast majority of people first glanced at the top sponsored listings. In eye tracking parlance, we call this a fixation, or a momentary pause of the eye. On Yahoo, 84% of the first fixations were on the top sponsored when they appeared, on Google it was 81%, and on MSN it was 87%. So, almost 9 out of every 10 people start looking at the search results page by at least glancing at the top sponsored.