Google led the explicit core search market in the United States in April with 65.4 percent of search queries conducted, according to comScore, Inc. (NASDAQ: SCOR). Yahoo! and Microsoft took the second and third spots with 15.7 percent and 13.9 percent of the U.S. market, respectively. Ask Network had 3.1 percent of the searches while AOL, Inc., was fifth with 1.6 percent.

According to comScore, more than 16.2 billion explicit core searches were conducted in April. Google had 10.7 billion searches while Yahoo! had 2.6 billion.

Google said revenues totaled $8.575 billion in the first quarter of 2011, compared with $6.775 in the same period in 2010. Advertising revenues made up 96% and 97% of revenues for the three months ended March 31, 2010 and 2011.

Advertising revenues made up 96% and 97% of Google's revenues for the three months ended March 31, 2010 and 2011. AdWords revolutionized Google's advertising, offering advertisers the chance to bid to display their ads when people searched for certain keywords in Google. An advertiser only pays when a user clicks on the ad.