Facebook Inc rose in late trading last week after Chief Executive Officer Mark Zuckerberg said he's addressing the missteps that have made it hard to reap the benefits of mobile advertising.

"Now we are a mobile company," Zuckerberg said in an on-stage interview at the TechCrunch Disrupt conference in San Francisco on Sept 12, his first since Facebook's initial public offering. "Over the next three to five years I think the biggest question that is on everyone's minds, that will determine our performance over that period, is really how well we do with mobile."

Mark Zuckerberg, chief executive officer and founder of Facebook Inc, speaking during TechCrunch Disrupt SF 2012 in San Francisco. Zuckergerg, addressing the company's stock slump for the first time since a May initial public offering, said growth in the coming years will hinge on the social networking site's ability to succeed with mobile products. [Photo/China Daily]

Shares in Facebook, based in Menlo Park, California, climbed as much as 4.8 percent as the remarks allayed concerns over the company's ability to generate sales from users who are increasingly socializing over handheld devices. The stock had plunged 49 percent since the May 17 IPO amid signs of slowing growth and executives' silence over plans to turn the tide.

"He struck an upbeat tone," said Colin Sebastian, an analyst at Robert W. Baird & Co in San Francisco. "Clearly, from his words, they are making progress in mobile."

Zuckerberg, who appeared at ease while trading laughs with his interviewer, for the first time elaborated on technical struggles that have impeded Facebook from creating a user- and advertiser-friendly mobile application. The company spent too long trying to build mobile products using a programming language known as HTML5, Zuckerberg said.

'Biggest mistake'

"The biggest mistake we've made as a company is betting too much on HTML5," he said.

Facebook is lessening its reliance on the tools and it has built an application better tailored for Apple Inc's mobile software, Zuckerberg said. It's also working on an application for Google Inc's Android system. New features will be available to the mobile service in the coming weeks and months, he said.

Based on the amount of time users spend on mobile, the company should make "a lot more money" via wireless devices than through desktops, Zuckerberg said. Mobile users also tend to be more interactive than desktop users, he said.

The stock extended its after-hours climb after Zuckerberg said Facebook is taking steps to strengthen search capabilities. The company is fielding about a billion search queries a day.

Search team

"We have a team working on search," said Zuckerberg, who was interviewed by Michael Arrington, a venture capitalist and the founder of the TechCrunch technology blog. "Search engines are really evolving towards giving you a set of answers."

Zuckerberg also said Instagram, the mobile photo-sharing service recently acquired by Facebook, has more than 100 million registered users. Facebook wants to help Instagram, which cost the company about $740 million in cash and stock, to grow to hundreds of millions of users, he said.

Facebook, which hasn't closed above the $38 IPO price since its first trading day, reported in July that second-quarter sales increased 32 percent, down from 45 percent in the previous three months. Facebook rose to as high as $20.36 in late trading on Tuesday, Sept 11, after earlier adding 3.3 percent to $19.43 at the close.

The share-price performance has been "disappointing" and it "doesn't help" in terms of employee morale, Zuckerberg said.

Still, Zuckerberg would rather Facebook be underestimated rather than lavished with praise, he said. That gives the company flexibility to make big bets on the future.

"Sure, maybe some people will leave," he said. "But I think it's a great time for people to join and a great time for people to stay and double down."