I have just rebuilt one site. It has been a solid earner for the last 12 years. I moved it from a bespoke PHP site to Drupal - only took 5 months!

I still used the same CSS framework (Zurb Foundation) and very similar layout. I even looked hard at how to make it better for tablets - as that appears to be a lot of my visitors.

Anyway, the short of it active views viewable has dropped from over 70% to near enough 50% since the change.

Aside from the small layout changes the only thing relating to Adsense that are different might be the ad slots have been shuffled around, i.e. the one I might have called top-responsive might now appear somewhere else.
Also, I have used media queries to hide / show ads (in line with Google's recommendations) to place ads differently for mobile / tabs etc.

To make it worse, every time I think I know what will improve it and make a change it actually gets worse?!

Any ideas?

Thanks,
Chris