SAN FRANCISCO — Google Inc. is offering to run the search engines of small Web sites for as little as $100 per year, marking the company's latest attempt to make more money off technology that already steers much of the Internet's traffic.

The service, scheduled to be unveiled today, is aimed at the millions of Web sites that either don't have search engines or are unhappy with the quality of their current search results, said Nitin Mangtani, a Google product manager.

The price for Google's "Custom Search Business Edition" will start at $100 annually to sift through up to 5,000 Web pages. Larger Web sites can pay Google $500 annually to search up to 50,000 Web pages.

That's a significant discount from the fees that Google has been charging for scaled-down versions of its Internet-leading search engine. The price for the so-called Google "Mini" — a combination of hardware and software introduced more than two years ago — starts at $1,995. More sophisticated iterations of Google's search engine cost hundreds of thousands of dollars.

Google has been offering a free version of custom search since last October to Web sites willing to show ads selected by the Mountain View-based company. The results produced by the free service direct traffic to Google's Web site.

Web sites that buy the new business edition will be able to block Google's ads. The search results also will be displayed on the customer's own Web site.

The discount service underscores Google's determination to build upon the immense popularity of its own search engine, which has become synonymous with looking things up online.

In June, Google's search engine handled nearly half of all online search requests in the United States, according to statistics released yesterday by comScore Media Metrix. Its closest rival, Yahoo Inc., was a distant second with a 25 percent share.

The advertising funneled through Google's search engine generates virtually all of the company's profits, which have totaled $5.8 billion since its initial public offering in August 2004.

In an effort to develop new sources of revenue, Google has been licensing its search technology and other software applications. To bolster its push into the corporate market, Google last week announced plans to buy e-mail security firm Postini Inc. for $625 million.

The expansion has only yielded modest dividends so far. Software licensing has accounted for just 1 percent of $22 billion in revenue since its IPO.

With its latest service, Google is betting it can attract millions of dollars in revenue by giving Web site owners a simple and inexpensive way to help visitors find merchandise or content.

Most small Web sites should be able to customize their own search engines on Google's technology in about 10 minutes, Mangtani said. The entire process can be completed online, as long as a Web site doesn't need more than 50,000 Web pages to be searched.