Agregamos los repositorios mediante:
| 0 1 2 3 | su - gedit /etc/apt/sources.list | 
Y copiamos al final:
| 0 1 2 3 | #firefox 4 deb http://mozilla.debian.net/ squeeze-backports iceweasel-4.0 | 
e instalamos desde un terminal:
| 0 1 2 3 4 5 6 7 | su - wget -O- -q http://mozilla.debian.net/archive.asc | gpg --import gpg --check-sigs --fingerprint --keyring /usr/share/keyrings/debian-keyring.gpg 06C4AE2A gpg --export -a 06C4AE2A | sudo apt-key add - apt-get update apt-get install -t squeeze-backports iceweasel | 
