The 18% cohort is dominated by frequent radio listeners and Internet junkies, with people most likely to visit a station's Web site when they're at work. According to the Media Audit figures, the top 10 cities where Internet users visit radio Web sites are, in order: Minneapolis, Seattle, Atlanta, San Francisco, Dallas, Chicago, Denver, Philadelphia, Salt Lake City, and Milwaukee.

Streaming audio is enjoying growing popularity on the Web, and radio broadcasters and ad sales networks have moved quickly over the last several months to bulk up their online sales capabilities. In July, Katz Media Group acquired Net Radio Sales, renamed Katz Net Radio Sales--allowing advertisers to deliver ads across a variety of audio and Web-based platforms, including hundreds of station Web sites in its digital network. The company also provides a variety of interactive ads to station Web sites.

Also in July, Ronning Lipset Radio announced that it had partnered with Corstarr to use its Adcor technology for delivering Internet radio ads. Adcor allows broadcasters to set up multiple radio channels and deliver ads across one or all of them, targeting audiences by demographic characteristics and daypart.

Meanwhile, TargetSpot has signed up a slew of big radio broadcasters for its online service, which allows advertisers to create and place streaming audio ads synced with banner displays on radio Web sites. TargetSpot's list of partners includes CBS, Entercom and Warp Radio.

Clear Channel Radio, the largest radio owner in the country, has led the way with an aggressive online strategy implemented by Evan Harrison, formerly vice president and general manager of AOL Music and the AOL Radio Network. After joining Clear Channel in November 2006, Harrison launched a makeover of over 900 Clear Channel station Web sites, rolled out new products including original video content, and reorganized the network of sites to facilitate ad sales.

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