By BARBARA ORTUTAYNEW YORK (AP) â¿¿ Facebook delivered fourth-quarter results above Wall Street's expectations on Wednesday and sought to show that it has finally transformed into a "mobile company" after rising to dominance as a Web-based social network. But its stock dropped in after-hours trading as investors placed more significance on the company's growing expenses rather than on its increasing user base and higher advertising revenue. "Everything was slightly better than expected," said Wedbush Securities analyst Michael Pachter. "I don't see anything here that would make me want to sell the stock." Nonetheless, Facebook's stock fell $1.11, or 3.6 percent, to $30.13 in after-hours trading following the earnings report. Facebook Inc. grew its revenue and increased the percentage of it that comes from mobile advertising â¿¿ a closely watched figure. But expenses also grew sharply. The company also said 2013 will be a year of "significant investments" and hiring as it focuses on long-term growth rather than short-term profits. The world's largest social media company earned $64 million, or 3 cents per share, in the October-December period. That's down 79 percent from $302 million, or 14 cents per share, a year earlier when it was still a privately held company. Revenue rose 40 percent to $1.59 billion from $1.13 billion, surpassing analysts' expectations of $1.51 billion. Advertising revenue grew 41 percent to $1.33 billion, increasing at a faster clip than in the third quarter, when it climbed 36 percent to $1.09 billion. Excluding special items, mainly related to stock compensation expenses, Menlo Park, Calif.-based Facebook earned 17 cents per share in the latest quarter. Analysts polled by FactSet expected lower adjusted earnings of 15 cents per share. "There were no major red flags," said Raymond James analyst Aaron Kessler. "I think expectations may have even been just a little bit higher" than analyst estimates indicated, which may be another reason for the stock price drop.