In the past, publishers weren't allowed to change AdSense ads in any way other than what could be done through the AdSense ad-code generator or Blogger's Add-a-gadget / Adsense tools.
Now, however, some changes are allowed, so you can do things like:
- Responsive design: creating a single webpage that adapts to the device on it’s being viewed on (eg laptop, smartphone or tablet).
- A/B testing: creating multiple versions of a page and comparing how they are used to see which page is the most effective.
- Setting custom channels dynamically:
- Ad tag minification: Enabling your site pages to load faster by reducing the amount of data to be transferred.
In several places, AdSense say that the goals of these changes should be to "maximize ad and user experience" - and most of their Terms and Conditions about what you're not allowed to do still hold, so it's clearly not carte blanche to make any changes you want.
Provided you have enabled a mobile template then responsive / adaptive website design isn't and issue which Blogger users have to worry much about - although there are some things you can and should do.
A/B testing is certainly relevant- and I'll be looking to see how much support their code offers for this.
Right now, I'm not sure how relevant dynamic custom channels and minification are for Bloggers - will be investigating this over the coming weeks.
See AdSense's help-centre article for details and the specific code snippets related to the these types of changes.
