Google sites accounted for 45.1 percent of September searches in the U.S., up from 44.1 percent in August and 43.7 percent in July, comScore Networks reported.

Yahoo sites were in second place, with 28.1 percent of searches in September, down from 28.7 in August and 28.8 in July, according to comScore. Microsoft sites were in third place with 11.9 percent of searches, also down from the previous two months. Fourth-place Ask was the only other top 5 search engine aside from Google to increase its share from the previous two months (see graphic).

Americans conducted 6.6 billion searches online in September, 2 percent more than in August - and 31 percent more than in Sept. 2005, according to comScore. Some 879 million toolbar searches were conducted in September, accounting for 13 percent of the total U.S. searches.