Somme funny man thought that it would be good to screw up the behavior of home and end keys in firefox on Mac. Nobody knows why and everybody is complaining. Also, the same genius have made the ⌘→ and ⌘← commands navigate in history instead of doing what they do in every other application which is “move to the end or beginning of the line”.
Oh well.. Luckily there IS a solution for this. The extension keyconfig will fix half of the problem. Get the keyconfing extension here and disable the incriminating keys. Many thanks to the author. Now you have working command keys. As for the home and end key, I fixed my problem in vimperator, since it is an extension I use on all of my firefoxes. Basically the idea is to remap home and end (along with +shift variants)) so they fire off the command+arrow commands. Here is the code, enjoy :
imap <Home> <M-Left> imap <End> <M-Right> imap <S-End> <M-S-Right> imap <S-Home> <M-S-Left>
Either run it in the vimperator command line and do a :mkvimperatorrc! or put it directly into your configuration file.