"The performance of the stock has obviously been disappointing," Zuckerberg said in an on-stage conversation with Michael Arrington, the founder of the TechCrunch Disrupt conference where he appeared. "We care about our shareholders. We are excited about this mission of being more open and connected. Over the next three to five years the biggest question that is on people's minds is how well we do with mobile."
When the company first sold stock May 18, it offered a price of $38 per share, but the stock quickly fell about 50 percent. On Tuesday, Facebook stock closed up about 3 percent to $19.43.
Facebook's first big investor, board member Peter Thiel, sold about 20 million Facebook shares last month, but last week, Zuckerberg said he won't sell any of his stock for a year. The stock has stabilized since its initial fall, though it has not been over $20 per share in a month.
Many stock analysts say that while Facebook, with more than 900 million active users, is giant, it is not an automatic money maker. Advertisers have complained they have less idea of whom they're reaching on Facebook than when they place ads -- attached to specific search words -- on websites such as Google.
Moreover, they say, Facebook may suffer as people increasingly use mobile devices to access their Facebook accounts. Ads do not readily catch attention on a crowded smartphone screen when users are looking for Facebook friends.
Zuckerberg promised to improve Facebook's mobile app.
When Arrington asked him about future Facebook products, Zuckerberg focused entirely on mobile. He said the company's biggest mistake was the way the company had coded the apps, using HTML 5 computer language instead of native code.
"We burned two years on it. It is really painful," he said of that decision. Facebook recently released a brand new iPhone and iPad app written in native code. Zuckerberg said the company is working on an app for Android phones, and said it "will be ready when it is ready."
While Zuckerberg didn't reveal much about future company products or plans, he did say there is a dedicated team at Facebook working on improving search within the site, so that Facebook can function as a search engine, competing with Google.
The interview ended with Arrington asking Zuckerberg if he is still having fun.
"It's not about fun, it's about mission," Zuckerberg said. "I'd rather be in this cycle where they underestimate us. ... I just want to build good stuff."