NEW YORK, Feb 25 (Reuters) - Microsoft Corp said on Monday it would test a new way to measure the effectiveness of Internet advertising in a challenge to an industry standard that has helped the likes of Web search leader Google Inc.

Microsoft's "Engagement Mapping" is due to begin in beta form on March 1 and departs from a standard that ties sales, leads and traffic to the last ad that a user clicked on online. Instead, it attempts to take into account all the Internet interactions that lead a consumer to buy a product.

Microsoft's new ad initiative follows its purchase of online marketing company aQuantive for $6 billion last year in an effort to capitalize on the fast-growing online ad market and better compete against Google.

The software maker is also in the midst of a $41 billion unsolicited takeover attempt of Yahoo Inc.

"The 'last ad clicked' is an outdated and flawed approach because it essentially ignores all prior interactions the consumer has with a marketer's message," said Brian McAndrews, senior vice president of the advertiser and publisher solutions unit at Microsoft.

McAndrews, formerly chief executive of aQuantive, has been charged by Microsoft to take greater responsibilities at the company's loss-making online services unit.

"Our Engagement Mapping approach conveys how each ad exposure -- whether display, rich media or search, seen multiple times on multiple sites and across many channels -- influenced an eventual purchase," McAndrews said in a statement. He was due to unveil the program later on Monday at an Interactive Advertising Bureau conference.

Microsoft advertising clients and partner agencies such as Citi Cards and Initiative Media have signed on for the program. Microsoft bought aQuantive for $6 billion last year. Initial results from the program are expected to be available before the end of the second calendar quarter of 2008.

(Reporting by Michele Gershberg, editing by Gerald E. McCormick and Dave Zimmerman)

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