Is a spoof site like msfirefox.com legal i.e. does using their trademarks and logos come under fair use or something?
are you wondering about the domain or just the content of the site? legally, parodies are covered under fair use. whether or not they could have their domain taken from them is another issue entirely.
yes, parodies are legal under fair use even when they're trying to make a profit. http://en.wikipedia.org/wiki/Fair_use some basic starting info there
I dont think the domain can be taken, because it's not confusingly similar, it actually helps perpetuate the idea of it being a parody site. Actually though, it'd be even funnier if both MS and Mozilla came after the domain