On the 40th birthday of the cell phone today, Advertising Age reports that eMarketer has increased its 2013 mobile advertising forecasts. Web marketing dollars are transitioning from traditional desktop to mobile ads faster than analysts had initially expected, fuelled by Facebook and Twitter's entrance into the mobile advertising market this year.

As internet and social media usage increasingly shifts to smartphones and tablets, mobile has become an essential part of the digital marketing mix. Aside from the need to put ads where audiences will see them, mobile also presents marketers with new advertising options such as location-based targeting and in-store promotional tie-ins. When developing a mobile marketing campaign, it's important that advertisers understand how owners use mobile devices and tailor their approach accordingly. Advertisers should utilize responsive design techniques so that ads appear properly on any screen size, integrate their message into the user experience so that users will take the time to engage with the ad, and consider providing incentives for busy mobile users to interact with branded content.

Read more about eMarketer's updated forecasts at AdAge.com.