I can't install IceCat on ubuntu 12.04

I want to install IceCat on Terminal but it doesn't work.

$ sudo add-apt-repository ppa:gnuzilla-team/ppa && sudo apt-get update && sudo apt-get install icecat -y
Cannot access PPA (https://launchpad.net/api/1.0/~gnuzilla-team/+archive/ppa) to get PPA information, please check your internet connection.

You can install pacage icecat from Trisquel's main repository:

sudo apt-add-repository "deb http://mirror.fsf.org/trisquel/ toutatis-updates main"
sudo apt-get update
sudo apt-get install icecat

Warning: I suggested toutatis version of Trisquel because It's based on Ubuntu 12.04 (As you mentioned in question). So sudo apt-get upgrade aftre adding repository cause add/remove/upgrade packages in current system

Hence,

Alternatively you may directly download deb from https://packages.trisquel.info : i386 or amd64 or choose appropriate release and package from Main page.

Extending @Pandya-s answer.

As mentioned, you can install icecat from Trisquel's main repository. This line adds the repository to your debian/ubuntu system:

echo "deb http://mirror.fsf.org/trisquel/ belenos-updates main" | sudo tee -a /etc/apt/sources.list.d/trisquel.list

Now you need to set up some trust for the repo (GPG keys). Trisquel signing keys can be seen here: https://trisquel.info/en/wiki/download-trisquel You should not trust me and should check the numbers on the official page, but I used this:

sudo gpg --keyserver keys.gnupg.net --recv-keys 0xE6C27099CA21965B734AEA31B4EFB9F38D8AEBF1
sudo gpg2 --export --armor B4EFB9F38D8AEBF1 | sudo apt-key add -

You have set up the repo. Theoretically, you're ready to install icecat. The trisquel repo is large though, you may want to limit packages that would be automatically installed. Use something like this:

sudo nano /etc/apt/preferences.d/trisquel
    package: *
    Pin: origin "mirror.fsf.org"
    Pin-Priority: 100

Now you're ready to go!

sudo apt-get update
sudo apt-get install icecat