Installing FireFox 15 (or latest version) on CentOS 6.3 (or 6.x) via yum

Distilled from http://www.if-not-true-then-false.com/2011/install-firefox-on-fedora-centos-red-hat-rhel/

(Optional) Backup current FireFox profiles

tar -cvzf $HOME/mozilla-firefox-profiles-backup.tar.gz $HOME/.mozilla/firefox/

Change to root user

su -

Install Remi repository

rpm -Uvh http://download.fedoraproject.org/pub/epel/6/i386/epel-release-6-7.noarch.rpm
rpm -Uvh http://rpms.famillecollet.com/enterprise/remi-release-6.rpm

(Optional) Check for available versions

yum --enablerepo=remi list firefox

If you already have an older version of FireFox installed, then UPDATE

yum --enablerepo=remi update firefox

Otherwise INSTALL

yum --enablerepo=remi install firefox

Done!