Microsoft Corp. on Tuesday launched its own Internet search engine and a multi-million-dollar marketing campaign meant to draw the attention of consumers away from its top rivals Yahoo Inc. and market leader Google Inc.

The new search service, available on the homepage of MSN, replaces Yahoo as the search engine for Microsoft's entertainment portal. Along with the launch, the MSN homepage has been redesigned to offer a simpler layout and a cleaner look and feel.

Microsoft has lagged behind its three biggest competitors in search. The company, however, plans to catch up fast through a major advertising blitz that's expected to cost 10s of millions of dollars, the Wall Street Journal reported. Microsoft has already spent $100 million to develop and market its Internet search business.

Microsoft said it expects to reach at least 90 percent of the consumers in the United States and several hundred million globally through its marketing campaign, which will include advertising on television, the web and print.

Marketing for Microsoft is pivotal because most web surfers have already fallen into a habit of using a particular search engine or two, and need to be enticed to change their behavior.

"The challenge is not only getting people to the site and getting them to use it once, but, to a certain degree, changing their habits," Gary Price, search analyst for SearcEngineWatch.com, said. "People are creatures of habit and they tend to do things a certain way and use what they've become familiar with."

As an example of how difficult it may be to get people to switch, a nationwide survey of search-engine users by the Pew Internet & American Life Project found that 87 percent have successful search experiences most of the time today, including 17 percent who said they always find the information for which they are looking.

Most of the features on Microsoft's search engine are also available on competitors' offerings. The company, however, has added a feature that uses the Microsoft Encarta digital encyclopedia to provide answers to questions, such as "who is Abraham Lincoln," as opposed to gathering results based on keywords.

"This is the infancy, or even pre-infancy, of search engines becoming answer engines for certain types of factual questions," Price said.

Nevertheless, one important area Microsoft will have to catch up in is local search, a major focus of its competitors, particularly Yahoo.

"Of the three, Yahoo's local search is the best," Price said.

Over the last six months, Yahoo has made significant improvements, including the addition of traffic information to its online local map service.

Local search holds strong revenue potential for search engines, since many web surfers look for products and services near their home or in cities they're visiting. In general, however, local search draws the most complaints from consumers, who often find that the results don't match their needs, according to web performance tracker Keynote Systems Inc.

Another area of fierce competition is in desktop search. All three rivals have released beta software that can be downloaded to the desktop and used to search files in a person's PC, as well as the web. The tools are viewed as important among search companies because people often begin web surfing with a search engine.

Microsoft on Tuesday also refreshed the beta of its desktop search utility with several enhancements that include faster indexing of email file attachments.