So Debian comes with a rather old Iceweasel version. Wich in terms of graphics and eventually security, can be quite boring and troublesome. So you can see after the initial update, what version does Debian get with regular repositories.
Like debian, also the Iceweasel project has backports. So instead we install the version testing branch of Debian, and potentially bork your system, we’ll use Iceweasel’s backports.
1. Go to http://mozilla.debian.net choose your desired version for Iceweasel. In this case I opted to go for the stable release
2. Add the line to your repository list
$ deb http://mozilla.debian.net/ wheezy-backports iceweasel-release
3. Install the mozilla keyring
We do this in case APT complains about the keys missing
$ wget http://mozilla.debian.net/pkg-mozilla-archive-keyring_1.1_all.deb $ sudo dpkg -i pkg-mozilla-archive-keyring_1.1_all.deb
4. Update and Install
$ sudo apt-get update && sudo apt-get install -t wheezy-backports iceweasel