“When I got to Yahoo, mobile was everyone’s hobby. It was no one’s job,” Yahoo CEO Marissa Mayer told Michael Arrington on stage today at Disrupt NY.

Ever since Mayer joined Yahoo in July 2012, mobile has been one of the company’s main focuses. And it turns out that the company is doubling down on mobile once again.

“Mobile is doubling on every traffic metric we have,” she said. But it doesn’t mean that Yahoo’s mobile strategy is already successful. Yahoo ended 2013 with no apps in Apple’s top 100. In other words, producing massive mobile hits is a long and difficult process.

We want to build the best mobile apps in the industry.

That’s why Mayer promoted Adam Cahan to be in charge of all things mobile. If things go well, it will be because of him. If they don’t, it will also be his fault. Centralizing everything like that could make things more difficult, but Mayer doesn’t see it this way.

“Every organization has a drawback,” she said. “I was talking to Eric Schmidt — there are some companies that go back and forth between a functional and divisional organization. In the end, it doesn’t matter. You shouldn’t spend too much time reorganizing.”

So now that Yahoo is going with this centralized strategy, the company hired a lot of mobile developers and designers — some of them thanks to acquisitions.

“I asked how many people do we have working on mobile engineering, they said ‘like a hundred.’ And I asked: ‘like an actual hundred, or like 60 rounded up to 100 to make me feel better?'”

There are now 500 people working on mobile working under Cahan. And the company has a clear mission statement when it comes to mobile. “We put Adam’s team together, it’s going to be a 2-year experiment,” Mayer said. “We have a tremendous set of app developers and app designers. We want to build the best mobile apps in the industry. I will revisit in two years about how we want to run it moving forward.”

“We want to be the world’s digital daily habit,” Mayer said. And having people spend more time in Yahoo’s apps fits pretty well.

In Mayer’s Yahoo, there are three areas of focus: search, mail and digital magazines. And the company released new design-oriented apps, such as Yahoo Weather, Yahoo Mail and Yahoo News Digest.

“Last year was the year we began making our investment in mobile,” Mayer said. “We were really proud of the new Yahoo News Digest, the new Yahoo Mail. You could see that engagement picked up. We think we’re making big strides in mobile. But we think there’s more to do.”

In particular, the News Digest app is an interesting example. “To Adam’s credit, I didn’t want to launch [Yahoo News Digest] because I didn’t think it was in our core applications.” Then, the company used the app internally (dog-fooding, as we call it). “People just loved it. 40 percent of people who download the app use it every day.”

So Yahoo will keep iterating on these apps and release new apps. It will also try another strategy — serendipity. One of the things that works quite well on desktop is that people go to yahoo.com to check their emails and end up reading Yahoo News.

“We want that serendipitous experience,” Mayer said. “We want to make our apps a little bit more fully featured.” In the next generation of Yahoo apps, you will be able to check your emails, read news and check the weather in a few swipes.

And then, there is Tumblr. Mayer thinks that Yahoo didn’t overpay for Tumblr, which it acquired for $1.1 billion. Now, Tumblr comes with sponsored content. But the user base is apparently reacting pretty well. “48 percent reshare sponsored content — it’s so good,” Mayer said.

Tumblr will also play an important part in Yahoo’s mobile strategy. Tumblr’s mobile team has always been really good at design. Mayer considers Tumblr as a communication tool. It will be one of the apps that will end up in the top iOS apps. “Those communication tools like Tumblr and Yahoo Mail will be among the top apps,” she said.

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