It may not. I had a copy of the old xelation skin that was made by the same creator of this skin and it also had tons of bugs in certain browsers. Wiredgamers has had tons of complaints on their skin that it don't work with mac os. I have noticed that on wiredgamers, all the complaints on the skin have been removed for some reason. I'm not sure what firebird is though.
I guess they do very little testing before they release any skins.