If you told your visitors that you required the use of firefox on your website and they couldn't use your website without using firefox and you including an adsense referral ad for firefox, if that against Adsense TOC/Policies?
No, a warning would pop-up that would say something like, "This website is incompatitible with your internet browser (*Their Internet Browser Info Here*). Please download FireFox. [FireFox button]
I am guessing there is some sort of rule against it, I would contact google about it before I tried anything.
Yeah but lying to people saying it only works in FireFox is wrong, and I doubt Google would okay you doing that.
You could get around it by saying "this site best viewed with Firefox...Download the latest version here!" or "To get the full experience..download the latest version of Firefox". I'd bet that this isn't against TOS..but Google's a strange bunch..so you might want to double check.