Nielsen's latest search-tracking numbers had good news for Microsoft and mixed news for just about everyone else. According to Nielsen, Microsoft had a small gain in search traffic, edging up to 13.8 percent of the total U.S. market in December from a previous 12-month high of 12 percent.

Google and Yahoo saw their shares of the U.S. market drop to 56.3 percent and 17.7 percent, respectively.

While Nielsen recently changed its accounting system of U.S. search, the firm pointed out that by any measure, Google has not seen a month-to-month decline of its market share since June.