Install firefox 5 in ubuntu

What’s new in Firefox 5 RC :

Added support for CSS animations
The Do-Not-Track header preference has been moved to increase discoverability
Improved canvas, JavaScript, memory, and networking performance
Improved standards support for HTML5, XHR, MathML, SMIL, and canvas
Improved spell checking for some locales
Improved desktop environment integration for Linux users
WebGL content can no longer load cross-domain textures
Background tabs have setTimeout and setInterval clamped to 1000ms to improve performance
The Firefox development channel switcher introduced in previous Firefox Beta updates has been removed

System Requirements

Linux
Software Requirements
Please note that Linux distributors may provide packages for your distribution which have different requirements.

Firefox will not run at all without the following libraries or packages:
GTK+ 2.10 or higher
GLib 2.12 or higher
Pango 1.14 or higher
X.Org 1.0 or higher (1.7 or higher is recommended)
libstdc++ 4.3 or higher

For optimal functionality, we recommend the following libraries or packages:
NetworkManager 0.7 or higher
DBus 1.0 or higher
HAL 0.5.8 or higher
GNOME 2.16 or higher

Installing Firefox 5

Open terminal
Application >> Accessories >> Terminal

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