Facebook CEO Mark Zuckerberg gave his first public interview after his tech company's rocky IPO and the disappointing stock performance that followed. Facebook's share price is now worth about $19 — half as much as it was priced back in May when its stock first went on the market.

Zuckerberg took questions from Michael Arrington at TechCrunch Disrupt, a San Francisco conference for startups. We watched and listened in to the talk in case you missed it:

Building a mission and business go hand-in-hand

When asked whether Facebook has a morale problem with the stock-price fluctuations, Zuckerberg said the price "doesn't help." But the CEO said this isn't the company's first up-and-down season.

"People at Facebook are used to the press saying good and bad things," he said. What motivates Facebook employees "is building stuff that they're proud of. This isn't just Facebook. This is universal ... It's a great time for people to stay and double down."

Going forward, it's all about mobile

"Now we really are a mobile company. All the code we write is [for] mobile," Zuckerberg said.

He even acknowledged writing his founder's letter to current and potential shareholderson his mobile phone.

"I do everything on my phone," he said. "A lot of people do."

The decision to move to a mobile-first strategy follows that of most technology companies, which note that mobile platforms are where users are spending more time.

"On engagement, we're already seeing that mobile users are more likely to be daily active users than desktop users," Zuckerberg said. "They're more likely to use Facebook six or seven days of the week."

Mobile platforms also present new and different opportunities for making money.

Profiting on mobile is more akin to how TV makes money

Ads have to be more integrated on mobile because, unlike on a screen, there's no right rail on which to put ads. Zuckerberg says Facebook's product teams are thinking about developing new features with advertising fundamentally integrated.

"I think we know that we're going to do well on that," he said. "The question is getting there."

Going all in on HTML5 was a major misstep

When it came to developing Facebook for various platforms, the company's decision to code in HTML5 was its biggest mistake, Zuckerberg said, costing it two years and ultimately not panning out.

"We were just never able to get the quality we wanted," he said.

After failing in its effort, the Facebook team had to start over and rewrite its applications code in "native."

Native applications are built using device-specific tools, which require specialized coding skills and have to be written for each platform. But the upside is they can do fancier things and are often faster.

"The apps are now going to be in better shape now," Zuckerberg said.

Workflow inside Facebook changed

In a part of the talk that will appeal to you systems and workflow techies out there, Zuckerberg explained that the company went from being functionally organized — with one head of engineering, one head of product — to product groups. Today, Facebook has a newsfeed group, a platform product group, etc.

"Now there's a person who owns each one of those," he said.

Zuckerberg said this organizational structure will lead to some exciting rollouts in six to nine months.

On Instagram: 'They're killing it'

Facebook bought photo-sharing site Instagram for a cool $1 billion this summer (though the value of the deal has fallen along with Facebook's stock), a move that led to mixed reviews for both companies involved in the deal.

But Zuckerberg says it was a marriage that benefited both sides. He explained that Instagram was starting to get a lot of distribution on Facebook, but didn't want to bet just on one company; Facebook, on the other hand, didn't want to help Instagram with an abundance of resources without gaining value.

So, eventually Zuckerberg decided they could just become one company.

"We're going to execute on the features we decided on early," he said. "We want to help it grow to hundreds of millions of users. But we have no agenda of making them go onto our infrastructure. ... I think it's primarily a waste of time."

Facebook is not making a Facebook phone

"It's so clearly the wrong strategy for us," Zuckerberg said.

He argued that if Facebook theoretically built a phone, it wouldn't move the needle for the social-networking company. The Facebook strategy he outlined is distinct from other tech companies that are getting into hardware. It's to build a system that's integrated into every major device people want to use, instead of building the devices themselves.

Search is an "obvious thing" Facebook would want to do in the future

Facebook's search feature already gets a billion queries a day without trying, Zuckerberg said.

"Most of it is people trying to find people, but others are people looking for brand pages or apps that links to commercial behavior," he said. "I think there's a big opportunity there."

He observed that the nature of search engines is evolving to give users a set of answers instead of merely a collection of relevant information.

"Facebook is uniquely positioned to answer questions that people have, like, what sushi restaurants have my friends gone to in New York lately and liked? ... These are queries you could potentially do with Facebook that you couldn't do with anything else, we just have to do it," he said.

Zuckerberg says there is a search team at Facebook, but won't say how many engineers are on the team.

For Zuckerberg, it's not about fun, it's about mission

With his anxious and speedy delivery on stage, it was unclear whether Zuckerberg was enjoying himself at all these days. But he said that's not the point.

"There are times when everyone in the world thinks what we're doing is awesome. ... There are times when people are superpessimisitic," he said. "I personally would rather be in the cycle when people underestimate us. I think it gives us latitude to go out and take some big bets and do some things that excite and amaze people."

He wants the legacy to be connecting to everyone in the world.

Zuckerberg only codes for fun now

Zuckerberg says he doesn't code to the main branch of Facebook anymore because he doesn't want anyone else to have to keep up with what he does.

"Everything I [do] ... breaks," he said of his programming.

He talks really fast

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