Anyway, here's the quick and easy way to get set up with 64 bit firefox. Start it by calling firefox25
mkdir ~/tmp cd ~/tmp wget ftp://ftp.mozilla.org/pub/firefox/releases/25.0/linux-x86_64/en-GB/firefox-25.0.tar.bz2 tar xvf firefox-25.0.tar.bz2 cd firefox/ sudo mkdir /usr/local/lib/firefox-25.0 sudo cp * -R /usr/local/lib/firefox-25.0 sudo ln -s /usr/local/lib/firefox-25.0/firefox /usr/bin/firefox25