Just use the following instructions to download and install Firefox addons on linux (Ubuntu).

Download Firefox 3.0 plugins & addons for linux
Visit official website to grab latest version & other pupalor addons & plugins. You can also use wget command to download.

$ cd /home/techgyaan/Desktop
$ wget 'wget http://releases.mozilla.org/pub/mozilla.org/addons/1843/firebug-1.3.3-fx.xpi'

Assign the System Administrator to give permission to the file to excute & install without admin rights.
# cd /home/techgyaan/Desktop
# chmod 755 firebug-1.3.3-fx.xpi
# chown -R techgyaan\username:techgyaandomain^users /home/techgyaan/Desktop/firebug-1.3.3-fx.xpi

Ask domain user to install addons & plugins without admin rights.
First start firefox

$ /usr/sbin/firefox &

Goto File in Firefox Main Menu–> Open File (ctrl+0)
Goto file location where you have download the plugins & addons.
It will popup with Firebug Addon install. Install the addons & enjoy thats it!

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