Ye, different browsers do things differently, it's what makes people go crazy trying to develop quality websites. Even version to version of the same browser layout pages differently.
Luckly Google never took the world by storm as google was hoping. On average, they have about 3% of the webbrowsers that come to the sites I run. Firefox is actually a bit more at about 12-15%.
As Fontyyy pointed out, the original style is still there, you can change back and forth in your profile settings.
Changing the forums has been a two purpose reason for me, the first was a give a fresher look to the forums (has been the same for the past 6 or 7 years since we opened them), the second was to give me a test bed to really learn divs rather then tables and css. been using divs and css for many years, but this allowed me to really deep dive and get a much greater understanding of the divs especially.
As expected, Andy was the first to email me with his displeasure
I switched him back to the old style. Who would have guessed he wouldn't like the new style. Guess well have to do a poll to see if those who like the new style vs old style has anything to do with their like/dislike for the MC21 vs MC28 
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Charles Gallant