Yahoo managed to stay in second place with a market share of 13.54 percent, down slightly from the previous months 14.28 percent. Microsoft’s Bing search engine came in third with 10.1 percent, up from 9.87 percent in August. Microsoft and Yahoo managed to grab a combined market share of 23.64 percent. That’s down slightly from 24.15 percent in the previous month.

Ask.com came in as a distant fourth with 2.37 percent, up a notch from the previous month when the Oakland based company grabbed 2.28 percent of the search U.S. market. Another trend shows that long search queries averaging five to eight words decreased 1 percent from August to September 2010. Two-word searches comprised with 24.02 percent of the majority of searches.

In an attempt to stem the slide, Yahoo recently introduced significant changes to the way it presents search results.  Users can now pull up articles, tweets, images, and video content and view trending topics. Yahoo is also rolling out a new image search engine and user interface that offers slideshows from photo sites like Flickr, along with friend’s public Facebook albums.

The engine has been launched with Google asking developers and businesses for feedback. Google said the infrastructure was updated to index new content on the web faster.

The public testing of the new Google engine comes two weeks after Microsoft struck a deal to replace Yahoo!'s search engine with Bing.

In a blog post, Matt Cutts, a principal engineer at Google and Sitaram Iyer, a staff software engineer, said: "For the last several months, a large team of Googlers has been working on a secret project: a next-generation architecture for Google's web search. It's the first step in a process that will let us push the envelope on size, indexing speed, accuracy, comprehensiveness and other dimensions.”

"The new infrastructure sits 'under the hood' of Google's search engine,” so Cutts, “which means that most users won't notice a difference in search results. But web developers and power searchers might notice a few differences, so we're opening up a web developer preview to collect feedback."

In a personal blog post, Cutts said that Caffeine was not specifically a response to Bing: "I love competition in search and want lots of it, but this change has been in the works for months. I think the best way for Google to do well in search is to continue what we’ve done for the last decade or so: focus relentlessly on pushing our search quality forward. Nobody cares more about search than Google, and I don’t think we’ll ever stop trying to improve."

Searches performed at Yahoo.com will be powered by Microsoft's new Bing search engine. Yahoo, in turn, will be responsible for attracting advertisers.

Microsoft said that it will pay Yahoo 88% of the revenue it gains from searches on Yahoo's sites. The software giant will also have the rights to integrate Yahoo search technology into its own existing Web search platforms.

The revenue sharing agreement will increase Yahoos operating income by about $500 million annually, according to a press release.

The deal will allow Microsoft to "create more innovation in search, better value for advertisers and real consumer choice in a market currently dominated by a single company", so Chief Executive Steve Ballmer.