You are incorrect. It does not bypass adblock on firefox. Yes, the ad shows, but that's because it does not trigger any of firefox's blocking rules (assuming Fanboy's list. I didn't check the others). He triggers chrome's by the element of name="google_ads_try". Firefox does not block elements of that name. Firefox's much more powerful plugin architecture allows Adblock Plus on firefox to actually prevent ads from loading; it doesn't insert css to hide them. As such, javascript to try and prevent css injection does absolutely nothing against adblock plus.

As a proof of concept, visit this site (it's his modified to hit adblock plus's Fanboy's List by adding ?bannerid=100 to the end) http://pastehtml.com/view/bstgyxtln.html . Turn on and off adblock and notice how, even though I left his anti-adblocking code in, it's helpless to stop firefox actually blocking it.