How to Install Firefox 4 in Ubuntu 10.04 and Ubuntu 10.10

Firefox 4 (stable version) will be released very soon and this post will show you how to install Firefox in Ubuntu 10.04 and Ubuntu 10.10.

1. Firefox Stable PPA provides the latest stable builds of Firefox for Ubuntu 9.10, Ubuntu 10.04 and Ubuntu 10.10

The PPA is a stable repository that will provide the latest stable version of Firefox 4.0. At the moment the PPA has no Build this version of Firefox, but when it comes out we can get the stable version from it.
You can add the PPA to your repositories, using the following commands:

sudo add-apt-repository ppa:mozillateam/firefox-stable
sudo apt-get update

After that, if you installed a version of Firefox, you should get an update on the latest version of Firefox 4 when it is released.
If you do not want to wait until Firefox 4 is officially released and uploaded to the PPA, can install Firefox 4 RC using another PPA.

2. Firefox Next PPA: Firefox provides alpha / beta / RC builds for Ubuntu 9.10 Karmic Koala, 10.04 Lucid Lynx and 10.10 Maverick Meerkat.

This PPA is not stable, but this is better than Mozilla Daily PPA builds, because it provides us with the latest official versions alpha / beta / RC and not daily builds.
Add the PPA and install Firefox 4 RC 1 using the following commands:

sudo add-apt-repository ppa:mozillateam/firefox-next
sudo apt-get update
sudo apt-get install firefox-4.0