Mozilla is currently on schedule to release Firefox 6 on August 16th but it looks like the final version has already been signed off and is unofficially available on 
Mozilla’s servers.
Installation in Linux:
1- Download :
For 32 bit use this command to download firefox6.0
wget ftp://ftp.mozilla.org/pub/mozilla.org/firefox/releases/6.0/linux-i686/en-US/firefox-6.0.tar.bz2
For 64 bit:
wget ftp://ftp.mozilla.org/pub/mozilla.org/firefox/releases/6.0/linux-x86_64/en-US/firefox-6.0.tar.bz2
2- Now extract and move the folder to /opt
tar xvjf firefox-6.0.tar.bz2
sudo cp -r firefox/ /opt/firefox
sudo rm firefox-6.0.tar.bz2
sudo rm -r firefox/
3- Make a Symbolic Link
“Backup” the old Firefox launcher:
sudo mv /usr/bin/firefox /usr/bin/firefox-old
Create a symbolic link pointing to the new Firefox version:
sudo ln -s /opt/firefox/firefox6 /usr/bin/firefox
Now you can start the firefox
