Here's what I did (using andyn's method): Download the linux version of firefox 3.5 from http://www.mozilla.com/en-US/products/download.html?product=firefox-3.

Here's what I did (using andyn's method): Download the linux version of firefox 3.5 from http://www.mozilla.com/en-US/products/download.html?product=firefox-3.5&os=linux&lang=en-US http://www.mozilla.com/en-US/products/download.html?product=... Untar and unzip firefox-3.5.tar.bz2: tar xjf firefox-3.5.tar.bz2 Move the new firefox 3.5 directory to /usr/lib: sudo mv ./firefox /usr/lib/firefox-3.5 Create a shell script to run firefox using andyn's params. Create a file (I called it firefox.sh) in /usr/lib/firefox-3.5/ with the following contents: #!/bin/bash /usr/lib/firefox-3.5/firefox -no-remote -P <profile_name> Note: Substitude <profile_name> with whatever you want to call your Firefox 3.5 profile; just make sure when prompted at first-run you create a new profile with the same name. Make the shell script executable: sudo chmod u+x /usr/lib/firefox-3.5/firefox.sh Simlink the shell script into the /usr/bin dir, or somewhere on your path: sudo ln -s /usr/lib/firefox-3.5/firefox.sh /usr/bin/firefox3.5 Run the script from the command line using: firefox3.5 Enjoy!