Sept. 2 (Bloomberg) -- Google Inc., owner of the most popular Internet search engine, plans to introduce a Web browser today to challenge Microsoft Corp.'s decade-long dominance of the market.

The program, known as Chrome, will isolate flawed Web pages so users can close them without shutting down the entire browser, and will make it easier to run other applications without downloading them to a computer, Google said.

The software opens a new front in Google's fight with Microsoft, whose Internet Explorer controls more than 70 percent of the browser market. Google is trying to parlay its success over Microsoft in online searches into an effort to court users who want e-mail, calendars and word processing through a browser instead of products such as Microsoft's Word and Excel.

``They're protecting the flank to make sure Microsoft can't encroach on search,'' said Roger Kay, president of research firm Endpoint Technologies Associates in Wayland, Massachusetts. ``This is another branding opportunity for them.''

Google climbed the most in more than four months in Nasdaq Stock Market trading. The stock added $16.41 to $479.70 at 9:42 a.m. and earlier rose as much as 4.1 percent, the most since April. The shares had declined 33 percent this year before today. Microsoft rose 41 cents, or 1.5 percent, to $27.70.

A test version of Chrome will be available for download in more than 100 countries, Mountain View, California-based Google said yesterday in a blog post.

$160 Billion

The market for Web-based software may reach $160 billion by 2011, including revenue from advertising, Merrill Lynch & Co. said in a May report.

``We realized that the Web had evolved from mainly simple text pages to rich, interactive applications and that we needed to completely rethink the browser,'' Sundar Pichai, vice president of product management, and Linus Upson, engineering director, said in the blog post.

Google began offering an online mail program in 2004, following with calendars, word processing, spreadsheets and presentation software. For Chrome, Google developed its own version of a programming engine designed to support applications that aren't possible with other browsers, the blog post said.

Representatives for Microsoft didn't immediately return phone messages today.

Explorer, Firefox

Microsoft's Internet Explorer has about 72 percent of the Web browsing market, followed by Mozilla Corp.'s Firefox with 20 percent and Apple Inc.'s Safari with 6.4 percent, according to research firm Net Applications of Aliso Viejo, California.

Microsoft, the world's biggest software maker, has led the browser market since 1999, when it passed Netscape Communications Corp.'s Navigator. Microsoft had about 95 percent of the market in 2004, when it began losing share to Firefox.

Google fielded 62 percent of U.S. Internet searches in July, about twice as many as Microsoft and Yahoo! Inc. combined, according to researcher ComScore Inc.

Microsoft, based in Redmond, Washington, released a new version of Internet Explorer last week for testing. The software lets users control whether it saves the sites they've visited.

Mozilla, also based in Mountain View, said last week it extended an agreement through 2011 to keep Google as its default search engine. The company is owned by the non-profit Mozilla Foundation.

Like Firefox, Google plans to release Chrome as open-source software, meaning programmers can edit the code and add their own features.

To contact the reporter on this story: Crayton Harrison in Dallas at tharrison5@bloomberg.net.

Last Updated: September 2, 2008 10:08 EDT