Yahoo, in a pilot program with Revenue Science, has begun to test the placement of cost-per-click text ads on web pages based on user behavior, using user data collected by Revenue Science, writes AdWeek. The program could eventually challenge Google's extensive AdSense network, which places ads based on website content. Yahoo's new effort instead targets ads to consumer behavior. Omar Tawakol, Revenue Science's SVP of marketing, said prior on-site behavior often yields better results than page content.

He said early results of the program, which began in the spring and can be seen on www.dogster.com and www.catster.com, are "very encouraging." A Yahoo spokesman confirmed the test but declined comment. The beta comes weeks before Yahoo is expected to release its own advertising network similar to AdSense. Yahoo now operates a small network, showing text ads on the Yahoo portal and few other sites. The network at present works similarly to AdSense, scanning a Web page for its context and then matching that to advertising.

Revenue Science in April launched a network that would allow advertisers to run behavior-targeting brand advertising campaigns across several sites. Late last year, Yahoo hired a cofounder of Revenue Science as its chief data officer.