News of Facebook's fourth quarter growth should drive home one very important lesson: Mobile optimization is key to the success of your business. 

Wednesday, the social media giant reported a 63 percent increase in revenue for the fourth quarter of 2013, to $2.6 billion, compared to Q4 2012, The Wall Street Journal reported. Facebook's earnings came as a surprise to many, particularly amid recent reports of the company's weakening and aging user base. So how did Facebook manage such healthy earnings? Its newfound strength in mobile advertising. 

According to the The New York Times, 53 percent of Facebook's $2.34 billion in Q4 advertising revenue came from iPads, smartphones, and other mobile devices. The results were in stark contrast to 2012, when the company's advertising revenue was driven by banner ads on desktops. In 2012, mobile advertising only accounted for 23 percent of the company's revenue. 

Facebook COO Sheryl Sandberg told the Times that the company "had the best mobile app out there," and that Facebook claimed one out of every five minutes users spent online. She added that the social network has made its advertising effective for marketers by tailoring ads to target specific demographics and simplifying the company's ad model.