Install lastest stable Firefox from PPA

<?php
$URL="https://raw.githubusercontent.com/panticz/installit/master/install.firefox.sh";
echo "wget $URL -O - | bash -";
echo "

";
$c = curl_init();
curl_setopt($c, CURLOPT_URL, $URL);
curl_setopt($c, CURLOPT_RETURNTRANSFER, 1);
echo htmlspecialchars(curl_exec($c));
curl_close($c);
echo "

";
?>

Global Firefox extensions folder
/usr/lib/thunderbird-addons/extensions/

OPTIONAL: install flash
wget http://fpdownload.macromedia.com/get/flashplayer/pdc/11.2.202.233/install_flash_player_11_linux.x86_64.tar.gz -O /tmp/install_flash_player.tar.gz
tar -xzf /tmp/install_flash_player.tar.gz -C /tmp
cp /tmp/libflashplayer.so /usr/lib/firefox-addons/plugins/

OPTIONAL, install german language pack
http://www.gtlib.gatech.edu/pub/mozilla.org/firefox/releases/3.6/linux-i686/xpi/de.xpi

Leo translate engine
http://dict.leo.org/pages.ende/toolbars_de.html

Gmail Notifier
http://www.nuko.org:4649/addons/temp/gmail_notifier-0.6.4.3.privateBuild1-fx.xpi

Links
http://www.daniel-ritter.de/blog/ubuntuzilla-immer-die-aktuelle-firefox-und-thunderbirdversion-unter-ubuntu