China's largest search engine, Baidu Inc., said Thursday that its net profits slid 0.4 percent year on year in the fourth quarter of last year to 2.78 billion yuan (460 million U.S. dollars). The slight drop was mainly due to climbing marketing costs, especially for its mobile products. The company's expenditures in sales, general business and administration surged 135.1 percent year on year to 1.86 billion yuan in the final quarter, according to an unaudited business statement. Its revenue surged 50.3 percent from a year earlier to 9.52 billion yuan in the final quarter, indicating healthy growth. Li Yanhong, the company's chief executive, said the company has made remarkable progress in the mobile business and established a leading position in the mobile market, including in search, mobile application distribution and location-based services. In the fourth quarter, mobile business accounted for more than 20 percent of Baidu's revenue, Li said. In 2013, the company's total profits edged up 0.6 percent to 10.52 billion yuan, and its total revenues soared 43.2 percent to 31.94 billion yuan.