Need example for theming individual ad groups

I have no trouble theming all advertisements using CSS but I can't figure out how to theme individual groups (such that block ads are left justified and content ads are centered). I know the documentation says groups can be themed by group ID but there is no example of the exact syntax for doing that.

Could you please update the documentation showing an example of having one or more specific themes for specific ad groups along with a generic theme for remaining advertisements? Alternatively I would even be happy if I could theme al embedded content seperately from ads displayed in blocks; not sure if that's doable?

I have banged my head against the wall for hours trying to guess the actual syntax.

Thanks for perhaps the most important and useful Drupal module ever! Generating nice revenues with it, and will do even more when I can start using different sized ads.