10 months ago, Google introduced, in beta, the AdSense responsive ad unit - it is still in beta, but many publishers have adopted it on their responsive design web sites.
A responsive ad unit works on sites that are responsive. Meaning, a site that auto adjusts based on the device accessing it, without changing the design much. I am not going to get into it in detail but in short, it is a recommended path for mobile sites.
The beta ad unit performs very well according to those trying it out.
A WebmasterWorld thread has some publishers praising it:
No complaints here. It's hands down my highest paying ad unit.
Been rolling them out to portions of my site and I'm seeing a nice bump up in CPC. It's still early, but I'm very encouraged by what I've seen so far.
At this stage of the day (6PM), the money from my responsive ads code has surpassed the money from the same page with 300x250 (earlier in the day). With less than 1/2 of the page views. For this day.
So overall, it seems responsive sites should be using this responsive ad unit.
Have you tried it? The results good? Let us know in the comments.
Forum discussion at WebmasterWorld.