Yahoo this week plans to unveil a new program designed to improve the size of its Web index and the relevancy of its search engine results, the Sunnyvale, California company said Tuesday.

The Content Acquisition Program (CAP) will allow for both free and paid inclusion of Web sites into the Yahoo index, Yahoo said.

CAP's paid inclusion portion is called Site Match and will be powered by the Yahoo subsidiary Overture. For a fee, Yahoo will ensure that a Web site is included in its index.

CAP is currently available in the U.S. and will be provided abroad later this year, a Yahoo spokeswoman said.

Site Match has no effect on where a participating Web site ranks in search query results. However, Yahoo will not distinguish in query results whether a listed Web site was included in its index for a fee or as part of Yahoo's free Web crawling activities, she said.

Some feel that search engines should make this type of disclosure, while others feel it's a trivial matter for users.

"We're on the side of it not being much of an issue. We've surveyed consumers on this topic and overall just 20 percent of online adults express any concern about mistaking paid listings for natural search results," said David Schatsky, a Jupiter Research analyst. "This new program should definitely provide a nice revenue stream to Yahoo. I don't expect any consumer backlash from it."

Yahoo does separate from its main query results what are known as sponsored search results, and clearly labels them as such. Sponsored search results are a sort of online classified ad companies pay search engines to display along with relevant searches. "That's a good practice to do that type of full disclosure because placement in sponsored listings is clearly promotional in nature," Schatsky said.

Ultimately, what search engine users want are relevant results, and they don't care very much whether those are in the main query results list or in the sponsored links section, Schatsky said. "The name of the game for Yahoo in search is ease of use and relevancy. If they provide those two elements, they will be successful with consumers," he said.

Site Match subscribers who submit less than 1,000 URLs pay the following annual submission fee: US$49 for the first URL, $29 for each of the next 9 URLs and $10 each for URLs number 11 through 999, the spokeswoman said. On top of that, subscribers pay a fixed cost-per-click of either $0.15 or $0.30 every time a user clicks on one of the subscribers' listings. Businesses that submit 1,000 URLs or more participate in the Match Xchange program at no annual fee and a fixed cost-per-click of up to $1.00, depending on content category, she said.

Participation in Site Match also guarantees companies that their Web site's information in the Yahoo index will be updated every 48 hours, said Diana Lee, another Yahoo spokeswoman. Web sites in Yahoo's regular index that don't participate in Site Match get their index information updated at different intervals, with some getting index updates on a daily basis, she said. Currently, about 99 percent of the Web sites in Yahoo's index come from the company's free Web crawling activities, and about 1 percent from the paid programs, Lee added.

Site Match will group under one umbrella paid inclusion programs from companies Yahoo has bought, including Inktomi, AltaVista and FAST, and clients of those programs will be migrated over to Site Match, Yahoo said in its Tuesday release.

Meanwhile CAP's free inclusion channel is called Public Site Match. Participants include government, academic and non-profit entities such as National Public Radio, the Library of Congress and the National Science Foundation. These will be able to add their online content to the Yahoo index. It's not a do-it-yourself submission process; those interested need to contact Yahoo to submit their Web sites and content.