Search giant Google, Inc., continues to lord over revenues from mobile ads. It took 49.3 percent of total mobile ad sales amounting to $17.96 billion in 2013, according to eMarketer.

Arch rival Facebook, Inc., took just 17.5 percent in 2013, which is a hefty improvement compared to its 5.4 percent share of worldwide mobile ad spending in 2012.

Facebook's mobile ad revenues are forecast to improve to 21.7 percent this year. In contrast, analysts expect Google's share to drop this year, albeit only slightly. But Google's sales share for 2013 was smaller than that for 2012 and a further drop will give Google two straight years of falling sales.

Google and Facebook together accounted for more than two-thirds of last year's $17.96 billion in mobile ad sales worldwide. Mobile ad spending worldwide rocketed skywards by 105 percent last year and is forecast to jump another 75 percent this year to $31.45 billion.

Analysts said Facebook is making a focused effort to make more money from the mobile market and that effort appears to be paying off, said eMarketer.

In 2012, just 11 percent of Facebook's total ad revenue came from mobile. Last year, that figure rose to 45.1 percent and could reach as high as 63.4 percent this year.

Facebook is keeping it close against Google and its $19 billion acquisition of smartphone messaging service WhatsApp confirmed its intent on becoming a pivotal player in the mobile world. Facebook's acquisition of WhatsApp reflects a structural shift towards mobile by Internet and related technology industries.

Microsoft also sees its future in mobile and put its money where its mouth is with a $7.5 billion takeover of Nokia's loss-making mobile phone division.