According to mobile advertisement firm AdMob’s Mobile Metrics report for February, the iPhone now accounts for one-third of all worldwide smartphone web traffic, and half—49.5%—of US traffic. Interestingly, the iPod touch ranked second in worldwide handset traffic, with 6.7%, following only the iPhone with 11.2%. Apple ranked second in worldwide handset share, with 17.9% of requests compared to Nokia’s 30.2%. In the US, Apple…