Microsoft's Bing search engine ranks second behind Google in the U.S. market, according to the latest data released by comScore Inc.

Bing and Microsoft's other websites fielded 2.75 billion search requests in the U.S. during December, (up 2 percent) followed by and Yahoo sites with 2.6 billion. Google still ranked first with 12 billion (up 3 percent).

These figures are translated into a 65.9 percent market share of the U.S. search traffic for Google, followed by Microsoft Sites with 15.1 percent and Yahoo Sites with 14.5 percent. Ask Network accounted for 2.9 percent of explicit core searches, followed by AOL, Inc. with 1.6 percent.

The flip-flop in the positions of Microsoft and Yahoo in Internet search was expected after their partnership announced in July 2009. The agreement has enabled Yahoo to save money by relying on Microsoft to provide the bulk of its search technology.

Even though it leans on Microsoft's technology, Yahoo hasn't totally abandoned search. It still offers some unique features within its results in hopes of persuading more people to search on its website instead of going directly to Bing.