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Yahoo CEO Marissa Mayer told audiences at the Yahoo Mobile Developer Conference in San Francisco Thursday that her company hit $1.2 billion in mobile revenue last year. With about 575 million monthly mobile visitors, that makes Yahoo "the third-largest mobile ad company in the world."

"This reinvention of mobile is perhaps the thing I'm most proud of as CEO," Mayer said. "The investment has paid off in terms of users, revenue and time spent. It outpaces not just our historic rate—not hard—but even also outpaced the industry rate."

Yahoo CEO Marissa Mayer speaks during her keynote at the 2014 Cannes Lions, June 17, 2014, in Cannes, France.
Didier Baverel | Getty Images

She also announced that there are now 500 people working at Yahoo mobile to revamp the app offerings. That is up from just 50 people two years ago.

In development news, the company announced the Yahoo Mobile Developer Suite. That will allow for app marketing and ad publishing, among other products.