According to Google AdSense program policies publishers are allowed to place only one ad unit on any mobile webpage.
Google added a new feature, according to which, you can choose to show adsense ads only to high-end devices(like iPhone)or to “All phones”.
By default ads are set to show only on iPhone and other high-end devices. If you like to show ads for all devices, then you have to choose “All phones” option from the drop down menu.
As always, we can show: “Text Only Ads”, “Image Only Ads”, or “Text and Image Ads(default)”.
Supported Ad formates(size):
320 x 50 Leaderboard
250 x 250 Square
200 x 200 Small Square
300 x 250 Medium Rectangle
We are waiting for more info on this, from the official website. And we guess that, all the mobile webpages, which have adsense ads will automatically be set to show ads only to high-end devices. If you want to make sure, to show ads on all the phones, then goto your adsense account and use the new code.