GNU IceCat, formerly known as GNU IceWeasel,is a free software rebranding of the Mozilla Firefox web browser distributed by the GNU Project. It is compatible with both the GNU/Linux and OS X (10.4 and 10.5) operating systems.
The GNU Project keeps IceCat in synchronization with upstream development of Firefox while removing all trademarked artwork. It also maintains a large list of free software plugins. In addition, it features a few security features not found in the mainline Firefox browser.
Icedove is an e-mail client distributed by the Debian project. It is based on Mozilla Thunderbird, but is made entirely of free software. With Icedove, the Debian project aims to provide a version of the Mozilla Thunderbird e-mail client which has not yet been kept in synchronization with upstream development of Thunderbird as originally planned. It removes the proprietary artwork and plug-in repositories used in the official release by the Mozilla Corporation, which are classified as non-free by free software advocates.
Install Icecat and Icedove on debian 7 (Wheezy)
Create sources.list file
sudo vi /etc/apt/sources.list.d/iceweasel.list
Add the following line
deb http://cdn.debian.net/debian experimental main
Save and exit the file
Now you need to download key and install deb package
sudo dpkg -i pkg-mozilla-archive-keyring_1.1_all.deb
Update the source list
sudo apt-get update
Install packages using the following commands
sudo apt-get install -t experimental iceweasel
sudo apt-get install -t unstable icedove