UPDATE2 - Microsoft abandons Yahoo acquisition

through innovative new services and strategic transactions with other business partners. While Yahoo would have accelerated our strategy, I am confident that we can continue to move forward toward our goals," Ballmer said in Saturday's statement.

"We are investing heavily in new tools and Web experiences, we have dramatically improved our search performance and advertiser satisfaction, and we will continue to build our scale through organic growth and partnerships," said Kevin Johnson, Microsoft president for platforms and services, in the statement.

As of the end of 2007's third quarter, Google had almost 25 percent of the U.S. Internet advertising market, up from almost 21 percent in 2006's third quarter, according to IDC. Meanwhile, Yahoo's share during this period dropped to 11.3 percent from 12.3 percent, while Microsoft's declined to 5.2 percent from 5.8 percent, according to IDC.

In search usage, Google held a commanding 62.4 percent of queries worldwide, followed by Yahoo in a very distant second place with 12.8 percent, according to comScore. Microsoft ranked fourth with 2.9 percent, after Baidu with 5.2 percent.

In November, Yahoo ranked first in the U.S. in display ad impressions with a 19 percent share, while Microsoft came in third with 6.7 percent, after News Corp.'s Fox Interactive (16.3 percent), according to comScore. Google took seventh place with 1 percent.