Yahoo Inc. on Wednesday launched in beta a service that enables small and medium-sized web sites to publish text-based ads and share in the revenue from Yahoo advertisers.

The service, which is only available during the testing phase by invitation, is meant to broaden the reach Yahoo can provide to its advertisers, Willan Johnson, general manager of Yahoo Publisher Network, said.

"What (advertisers) are interested in is getting leads to their web sites and generating sales," Johnson said. "This is a way of getting advertisers more leads by extending our distribution to small and medium-sized publishers."

Search rival Google Inc. has long offered self-service publishing through its AdSense service, which contributed $630 million, or 46 percent of total revenues generated in the second quarter ended June 30.

Self-service advertising and publishing, in general, is a trend in the online search industry.

Ask Jeeves, which is owned by IAC/InterActive Corp, said this week that it would let small and medium-sized advertisers bid online for keywords. The search engine also started offering tools to let advertisers manage campaigns.

Microsoft Corp. in March announced that it plans to offer advertisers on its MSN portal a variety of self-service features, including buying keywords and offering tools for campaign management. In announcing the plans, chief executive Steve Ballmer hinted that changes were possible in its current partnership with Yahoo. MSN publishes ads from the Sunnyvale, Calif., portal.

"We still see opportunities to partner there. We're having discussions. But we think it's also important that even while we maintain what has been a very good partnership for both companies, there are places where we have ideas to innovate," Ballmer said.

Before the launch, Yahoo distributed its ad links through its large publishers, which include CNN, ESPN, MSN and others, Johnson said. Those deals would continue to be made through account managers.

The new service also lets publishers feed content to people with personal Yahoo homepages. The content distribution is handled through RSS, or really simple syndication, a format for distributing news or other content updates.

For offering an RSS feed, Yahoo provides the code in the form of an "Add to My Yahoo" button that publishers can post on their web sites.

Yahoo also is offering small and medium-sized web sites the option of adding Yahoo search. A travel site, for example, could include a Yahoo search link on a blog on Hawaii, giving readers the option of getting more information on the island state.

Neither service provides any revenue to the publisher, but that could change, Johnson said. The search service could one day offer revenue sharing, if a user clicks on a Yahoo advertiser's link, and the company is considering the option of allowing publishers to send advertising through the RSS feeds.

Future services include allowing publishers to add a "Save to My Web" button to their sites, so Yahoo subscribers could save pages through the portal's personal search engine service. The product lets subscribers save web pages in order to find them quicker at a later date.

Yahoo expects to complete the initial testing phase of the service and make it generally available by the end of the year.