UPDATE 1-Yahoo buys behavioral ad firm for $300 mln

(Adds details of deal, executive comment, context, byline)

By Eric Auchard

SAN FRANCISCO, Sept 4 (Reuters) - Yahoo Inc (YHOO.O: Quote, Profile, Research, Stock Buzz) has struck a deal to buy BlueLithium, the fifth-largest U.S. online advertising network, for $300 million in cash, in the latest move to consolidate the behavioral ad targeting market.

BlueLithium is a three-year-old company that specializes in the fast-growing market for technology that tracks consumer behavior as users move from site to site in order to deliver more relevant ads.

The deal, announced on Tuesday, bolsters Yahoo's existing behavioral ad targeting efforts with its 250 million-strong base of Yahoo Mail users and Yahoo Travel, an analyst said.

BlueLithium is an invitation-only network of roughly 1,000 sites that adds to Yahoo's growing ad network. Besides Yahoo's own properties such as news, sports and travel, other parts include the Yahoo Publisher Network of affiliated sites and Right Media Exchange, which reaches a wider range of sites.

BlueLithium, a venture capital-backed company based in San Jose, California, serves up ads to 145 million unique visitors a month, the companies said, citing data from online measurement firm comScore Inc. It is number five among U.S. online ad networks and the second-largest in Britain.

"This really gives us the ability to (deliver) more relevant advertising to consumers not only on the Yahoo network but also off the network," Todd Teresi, senior vice president of the Yahoo Publisher Network, said in a phone interview.

The deal comes a little over a month after Time Warner Inc's (TWX.N: Quote, Profile, Research, Stock Buzz) AOL LLC unit said it would buy Tacoda Inc, paying $275 million in cash, according to a source close to the deal.