Edwin Perello discovered that Bing, the Microsoft search engine, could find addresses in his rural Indiana town when Google could not. Laura Michelson, an administrative assistant in San Francisco, was lured by Bing’s flight fare tracker. Paul Callan, a photography buff in Chicago, fell for Bing’s vivid background images.

Like most Americans, they still use Google as their main search tool. But more often, they find themselves navigating to Microsoft’s year-old Bing for certain tasks, and sometimes they stay a while.

"I was a Google user before, but the more I used Bing, the more I liked it," Callan said. "It’s more like muscle memory takes me to Google."

Bing still handles a small slice of Web searches in the United States, 12.7 percent in June, compared with Google’s 62.6 percent, as measured by comScore, the Web analytics firm. But Bing’s share has been growing, as has Yahoo’s, while Google’s has been shrinking.

And while no one argues that Google’s dominance is in immediate jeopardy, Google is watching Microsoft closely, mimicking some of Bing’s innovations – like its travel search engine, its ability to tie more tools to social networking sites and its image search – or buying startups to help it do so in the future.

Google has even taken on some of Bing’s distinctive look, like giving people the option of a Bing-like colorful background, and the placement of navigation tools on the left-hand side of the page.

The result is a renaissance in search, resulting in more sophisticated tools for consumers who want richer answers to complex questions than the standard litany of blue links.

The competition is a remarkable and surprising twist: Microsoft, knocked around for so long as a bumbling laggard, has given the innovative upstart Google a kick in the pants. As the search engines introduce feature after competing feature, some analysts say they have set off an arms race, with the companies poised to spend whatever it takes to win the second phase of Web search.

"There is a Cold War going on," said Sandeep Aggarwal, senior Internet and software analyst at Caris & Company, who watches both companies. "Clearly, you can see how Bing’s competition is forcing Google to try and catch up in some places."

Google officials agree there is more competition, but say they are not simply reacting to the younger search engine.

Google’s new features have not been in response to Bing, said Marissa Mayer, the company’s vice president for search products and user experience. "A lot of these things have been in the works for a long time," Mayer said. "Left-hand navigaton we worked on for almost two years. We wanted to make sure we had it exactly right."

Microsoft’s gains are far from staggering. Its share of searches has grown to 12.7 percent, from 8 percent, since it was introduced in May 2009, and Yahoo, which has a search deal with Microsoft, still handles a larger share of searches than Bing. And in the newest search frontier, mobile search, Google has even more market share than on the Web at large.

Still, Bing’s gains have impressed analysts who have watched Google fend off repeated assaults on its lucrative search and ad business, which accounts for some 95 percent of its revenue.

Building a more comprehensive, faster and more accurate search engine than Google is a daunting challenge, and a long list of big companies and startups have failed in their attempts. Microsoft endured plenty of ribbing as it spent years building and then scrapping search systems meant to help it compete against Google. But it kept experimenting until it found a way.

Microsoft has spent billions of dollars building the computing centers needed to power search and advertising systems and acquiring startups with niche expertise. In addition, it has thrown money at consumers, through cash-back programs on purchases, and at partners willing to promote Bing ahead of Google. Over the last year, Microsoft’s online services division lost $2.36 billion on revenue of $2.2 billion.

With Bing, Microsoft has tried to attract people like Callan by excelling at answering frequently asked questions, like those related to travel, health, shopping, entertainment and local businesses. For example, Bing has flight search and prediction tools that reveal how prices for a certain route fluctuate, and advises customers whether to buy or wait. Bing Health uses data from sources like the Mayo Clinic and Healthwise.

The hope is that "somebody would come back just for that and then, down the line, they would do other types of searches, too," said Danny Sullivan, a longtime industry analyst and editor in chief of the blog Search Engine Land.

People do not always want to click on links and dig through pages to hunt out information, so when Bing started in May 2009, it pulled relevant information and stuck it on the top and left-hand side of the results pages. Search "Angelina Jolie," for instance, and see a slide show and a list of her movies on top and related links on the side.

"We said, ‘Let’s change the entire way we lay out pages,"’ said Yusuf Mehdi, a senior vice president for Microsoft’s online audiences business. "We will not be shackled by blue links."

Google, meanwhile, has quietly introduced its own new features that have in several instances looked a lot like Bing’s.

For example, in May, it too added the left-hand navigation tools – though Mayer of Google pointed out that many of the tools had already been available, just not easily visible from the search page.

"Certainly there’s been increased competition in the space," Mayer said of Bing. "When there’s more competition, everyone’s search gets better, that serves the users a lot better."

Bing’s travel tool uses technology from Farecast, which Microsoft bought in early 2008. In July, Google announced plans to acquire ITA Software for $700 million; ITA makes the same comparison shopping software for flights that Bing’s Farecast uses.

Then there is the look of the main search pages for each site. Microsoft has argued that the vivid images ever-present behind the Bing search box have helped its appeal; young people and women have shown a particular fondness for Bing. In June, Google offered people the option to have a colorful background image like the Golden Gate Bridge on its main search page rather than the stark, white page that helped make Google famous.

Google has also played catch-up to Microsoft in offering ways to search for and digest more images in one go, and has trailed in adding some tie-ins to social networking sites.

"Google’s new innovations have come at a slower pace," Aggarwal said. "There was no one challenging Google until Microsoft decided it was a business they would not give up."

Still, Sullivan and other analysts also say Google has been making many significant but subtle behind-the-scenes changes that make it better at responding to obscure and complex queries. Google made 500 tweaks to its secret search algorithm last year and introduced personalized search, which customizes results based on what users frequently click on.

Google executives often chide Microsoft that it overengineers software like Office and bombards people with needless features. But now Google has swapped its clean, simple approach to search in favor of a feature war with Microsoft.

"Google seems to do things because Bing has done something," Sullivan said. "It’s a kind of knee-jerk thing – we have to do this product now because we don’t want people to think we’re weak."

© 2010 The New York Times Company