• by Mark Walsh  @markfwal, October 1, 2009

The iPhone continued its global march in August, with the iPhone OS growing from a 33% to 40% market share worldwide, according to the latest monthly metrics from mobile ad network AdMob. The increase comes at the expense of older operating systems like Symbian and Windows Mobile.

The iPhone and iPod touch accounted for 27% of handsets used in the network, just ahead of Nokia, with 24%. Though Nokia's share has been declining, it continues to have 12 of the top 20 smartphones. The N97 and 5800 XpressMusic touchscreen devices were the fourth and fifth most popular smartphones in Western Europe. Nokia also continues to have a dominant in all regions outside North America, especially Asia and Africa.

AdMob also noted that Android is growing quickly in North America and Western Europe, with the HTC Magic (T-Mobile myTouch) becoming a top 10 smartphone on both sides of the Atlantic. Ad impressions on the Android increased 17%, but that growth rate was down significantly from the 50% gain n July.

In the U.S. Palm's webOS operating system, which powers the Pre, also had a strong showing, generating 9% of all smartphone ad impressions. Worldwide, smartphone impressions increased 9% to 10.6 billion. AdMob's network spans 9,000 publishers and 3,000 mobile applications globally.