Google has integrated their mobile ad component into the core interface of AdSense.
You can now generate the ad codes for both desktop and mobile websites from the same interface now.
Google suggests that you start using the newer code from this updated dashboard for your mobile web apps.
Google for now is automatically converting desktop ads to mobile ads on compatible mobile devices.
The new AdSense ad code automatically formats the ads for the device. We will continue to support high-end ad requests from our AdSense for mobile content product until May 1, 2012. We strongly encourage publishers who have designed mobile web pages for high-end devices to use the new AdSense ad code to avoid disruptions to service. Note that publishers with mobile websites built for WAP browsers should continue to monetize using AdSense for mobile content.