This seems very un-Google like, to be showing a little thumbnail of the pages in the search results page. It slows down the pages, its a graphic and its not so clean. One member at Cre8asite posted a topic named New Google SERP Display!, where he posts a screen image of what he is seeing at Google from his home on his Firefox browser. Could it be adware? Or is it Google really testing this out on some computers?
