The new Ad format by AdSense size of 320x100 has just announced a couple of hours ago, now you can add this to your website. Just take a look this banner below this would be the actual look of the ad size you can inject to your own website.
Steps how to create the new ad format:
- Visit "My Ads" tab in your AdSense account
- At the sidebar, choose “Ad Unit” under "Content"
- Click +New ad unit
- From the Ad Size top down menu you can choose the new format 320x100