Yahoo! plans to invite about 2,000 smaller publishers into the new offering, Yahoo! Publisher Network, before expanding further by the end of the year, said Will Johnson, general manager-vice president of Yahoo! Publisher Network Online.

At launch, the program is designed for publishers whose sites receive fewer than 20 million page views per month, said Johnson. The initial publishers will represent a wide range of sites, including e-commerce, travel and car verticals, and Web logs. To date, Yahoo! has been testing the program via its own employees who have blogs.

The new offering marks a significant expansion of Yahoo!'s existing ContentMatch, which allows marketers to buy pay-per-click ads on the largest sites, such as CNN, ESPN, and Viacom, said Johnson.

Initially, advertisers who participate in ContentMatch will be able to bid to appear in the new network. Yahoo! will share the pay-per-click revenues with the publishers.

Within the next few weeks, Yahoo! also will include a feature that enables publishers to suggest certain ad categories. "We're giving them some way of really influencing those ads," Johnson said.

For example, said Johnson, a music site publisher might know that the site's audience is interested in travel. That publisher will be able to go into a user interface and tell Yahoo! to serve travel ads to his site, or to specific pages within his site.

This feature raises the question of whether the ads are still "contextual." But Johnson indicated that ads in categories selected by publishers are likely to be relevant for the audience. He added that computerized contextual crawlers are limited by the content on the page, which might not be as "deep or rich" as the site's complete offerings.

Johnson also indicated that the feature was experimental for now, adding that Yahoo!'s algorithm will "learn over time what's getting clicked."

And Jupiter Research analyst Gary Stein said that giving publishers some input into which categories of ads are right for their sites makes sense. "That's the smartest piece of the whole thing," he said. "Publishers generally know their audience."

Bryan Wiener, president and chief operating officer of 360i, a performance marketing firm, said he thought advertisers would be interested in the service. "Only a small fraction of online consumers' time is spend on search--the rest is on content and services," he said. "Any program that helps offer additional targeted media on the rest of the Web is great for marketers."

In some ways, Yahoo!'s new platform benefits from Google's two years of experience with AdSense. For instance, after launching, Google decided to give publishers more control over ad formats and colors. Yahoo! intends to incorporate that enhancement by allowing publishers to choose the appearance and placement of the ads, so they don't look out of place on the site.

As with Google's AdSense, Yahoo!'s publishers will be able to block certain advertisers, such as those that compete with their businesses. Participants in Yahoo!'s network can restrict ads from up to 200 URLs--the same number that Google allows AdSense publishers to ban.

Yahoo! also plans to syndicate its own content, such as its music videos and job listings, to other publishers within the network.

Reporter Gavin O'Malley contributed to this article.

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