Not surprisingly, Google's share of the search-engine market continues to grow. Google earned 65.4 percent of the market in October, compared to 64.9 percent in September, according to comScore.

Microsoft is gaining momentum, thanks to its new Bing decision engine. Microsoft's total share of the U.S. search market rose to 9.9 percent in October. That's half a percentage point higher than comScore's September rankings.

Yahoo was the big loser in October. Despite Yahoo's continued investments into innovative features, the once-dominant search engine slipped to 18 percent market share compared to 18.8 percent in September.

Yahoo's Cause for Concern

Microsoft seems to be gaining momentum at Yahoo's expense. Microsoft has steadily watched its search-engine ratings rise since it launched Bing in June. Microsoft hedged its search-engine bets by inking a search-partnership deal with Yahoo in July to target Google. Still, the two search companies combined have less than half the market share Google boasts.

Yahoo may have cause for concern. At 18 percent, the company is sinking to new lows. In September, Yahoo launched a global brand campaign to realign its business around simplifying and enhancing the web experience for people around the world.

As part of that rebranding effort, Yahoo launched a new Yahoo "search experience" that works to make search more personally relevant. The new design features intelligent search results that aim to make it easier to see results from more sites, along with a search-assist expansion tool on the left-hand column of the page that lets users explore concepts related to the search query. But the new design wasn't enough to stem the tide of Yahoo's losses.

Bing's Big Month

Meanwhile, Microsoft has been building Bing's features. In June, Microsoft launched a new search destination for travelers called Bing Travel to help consumers make smart travel decisions. Bing Travel aims to reduce the amount of time consumers spend searching for travel information by presenting comprehensive results in one place, and to help consumers make more informed decisions with tools such as Price Predictor and Rate Indicator.

In September, Bing launched Visual Search, a new way for consumers to formulate and refine their search queries through imagery, particularly for sets of results that tend to be more structured. Visual Search lets users scroll through image galleries or do a one-click refinement using quick tabs on the left that are relevant to the results. And Bing Maps, Microsoft's mapping program, got an overhaul last week.

According to Greg Sterling, principal analyst at Sterling Market Intelligence, Bing's continued growth reinforces that it does have traction in the market. But Bing may not be making Google all that nervous. "Interestingly, Google doesn't appear to be suffering," he said. "It's Yahoo, AOL and Ask that are apparently seeing losses."