Add Repo to the Kubuntu Source list

Open file /etc/apt/sources.list on vi or any text editor with sudo

ex sudo vi /etc/apt/sources.list

Add the following lines at the end of the file

'deb http://ppa.launchpad.net/ubuntu-mozilla-daily/ppa/ubuntu jaunty main'
'deb-src http://ppa.launchpad.net/ubuntu-mozilla-daily/ppa/ubuntu jaunty main'

Run this command on konsole

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 247510BE

open start->system settings->computer administration->add or remove software
on the search box type firefox-X.x

Select the package from the list below to install and enjoy :)