“Right now, the focus is almost entirely on improving the user experience,” Mr. Lanzone said. “This is the product that, to date, we are the most proud of. It is going to have a huge impact for people who use Ask.”

For his part, Mr. Diller said AskCity was a demonstration of Ask’s role in helping tie together the disparate properties owned by IAC.

AskCity is “a really good service that is dependent on the information from all these IAC sites, which is the raison d’être of the company itself,” Mr. Diller said, adding that over time, other IAC entities, which include HSN, LendingTree.com, Evite and Match.com, will be more tightly integrated with Ask.

Accounting for 5.8 percent of all the searches in the United States in October, Ask has edged out AOL to become the fourth most popular search engine, according to comScore Media Metrix. By comparison, Google had 45.4 percent of all searches, Yahoo 28.2 percent and Microsoft 11.7 percent.

Data from Nielsen NetRatings, which measures only searches on Ask.com, not on related sites in the Ask network, shows that Ask’s use grew 25 percent in October from a year earlier, the second highest rate of growth among the major search engines, after Yahoo.

The turnaround of Ask began long before Mr. Diller acquired the company. After the collapse of the dot-com bubble, shares of Ask Jeeves dropped below $1 and the company was close to extinction. But in 2001, it sowed the seeds of its rebirth when it spent about $4 million to acquire Teoma Technologies, a small company in New Jersey that had developed well-regarded search technology. A year later, Ask Jeeves got a lifeline from Google, which cut a deal to place ads next to Ask Jeeves search results.