"I think the biggest mistake we made as a company was betting on HTML 5 instead of native," he said.

"It's not that HTML 5 is bad," Zuckerberg said, and he's optimistic about the technology in the long term. But after Facebook decided to develop for the Web first, its mobile strategy suffered.

"But we're coming out of that; the [new] iOS app is out and the [new] Android will be out soon," he said. Asked later to be more specific about timing for the Android app, he said: "It will be ready when it's ready."

Search is another big opportunity for the company, according to Zuckerberg. Facebook fields about a billion search queries a day, he said. They are mostly people searches, but also searches for company brand pages and applications.

"I think Facebook is uniquely positioned to answer a lot of queries people have," he said. "Like, 'What sushi restaurants have my friends gone to in New York in the last six months and liked?'"