On its 5th birthday, Squirrel Hill-based Web searching company Vivisimo Inc. gave the city a birthday present.

Vivisimo has donated the use of its Web-searching tool, dubbed Clusty, to the city of Pittsburgh Web site, at www.cityofpittsburgh.net. Clusty provides lists of relevant Web pages, much as Web search engine Google does, but also creates folders dividing the results into categories.

For instance, a search of the city's Web site for information on parks, using Clusty, yields 1,119 Web pages. That's a lot to scroll through. The folders, though, break those pages down into categories like park facilities, park maintenance, movies in the park and more.

"It's a really convenient tool for users out there to go directly to what they want," said Howard Stern, the city's chief information officer. He said an average of 4,300 people per day use the city's Web site, which includes 2,100 pages and links to many other sites. Clusty searches both the city Web site and the linked sites.

A separate search field allows users to search the entire Internet using Clusty.

"It's our city, and we decided we should give something back," said Vivisimo Chief Executive Officer Raul Valdes-Perez. Installing Clusty on a city Web site would cost "well into six figures," he said, but Vivisimo is doing this for free.

Vivisimo announced the gift at the grand opening of its new headquarters at 1710 Murray Ave. Vivisimo's clients include America Online, which uses the technology in its search functions; large corporations; and federal departments.