By BARBARA ORTUTAYNEW YORK (AP) â¿¿ A year ago, Facebook was just testing the waters of mobile advertising, causing plenty of headaches for investors ahead of its massive initial public offering. It has since eased those worries. On Wednesday the world's biggest social networking company said nearly a third of its advertising revenue came from mobile in the first three months of the year, helping to push total revenue up 38 percent to surpass Wall Street's expectations. "They are making the transition to mobile faster than anyone anticipated," said Sterne Agee analyst Arvind Bhatia. "It seems like they are delivering." Facebook Inc. said Wednesday that its net income was $219 million, or 9 cents per share, in the January-March period. That's up from $205 million, or 9 cents per share, in the same period a year ago, when it was still private. Revenue grew to $1.46 billion from $1.06 billion, above analysts' expectations of $1.44 billion. Excluding special items, mainly related to stock compensation expenses, Facebook earned 12 cents per share, matching the average of analyst expectations, according to FactSet. Menlo Park, Calif.-based Facebook said that its mobile advertising revenue was 30 percent of its total ad revenue in the first quarter, amounting to $375 million. That's up from 23 percent, or $306 million, in the fourth quarter. In the third quarter â¿¿ the first time it disclosed such figures â¿¿ the company generated 14 percent, or $153 million, of its advertising revenue from mobile. Investors had been worried about Facebook's ability to grow mobile revenue since before its initial public offering in May 2012. That's because although the number of people who access Facebook on smartphones and tablet computers has been growing quickly, Facebook didn't begin showing ads to those users until last year. David Ebersman, Facebook's chief financial officer, said most advertisers did not specify that their ads be shown only on desktop computers or only on mobile devices, "rather they put their ads into our system and allow us to show the ads on whatever device where the ads will perform best."