Do users click on adsense ads on mobile phones very much or is it the same as desktop?
I ask because a lot of my site shave 728 size ads.
how would you recommend inserting a 468 size into it with a mobile css file?

From what I witnessed , many sites have a narrowed down their horizontal nav menu on top; reducing from 7 items to 3 or 4 item menus (hence the lessened width 480), no floats, and slightly bigger font sizes.