Running multiple version of firefox

If you want to run multiple versions of firefox on same machine, follow below steps:

1. Close your all running instances of firefox
2. Download older versions of firefox from http://www.oldversion.com/Mozilla-Firefox.html and do a custom install, install them on a specific version directory. For example I installed them as below:
C:\Program Files\Mozilla Firefox_6.0.2
C:\Program Files\Mozilla Firefox_7.0.1
3. Create profiles for every version by following steps:
    A. Goto Run command (or press WINDOWS+R)
    B. C:\Program Files\Mozilla Firefox_6.0.2 -P
    C. It will open a profile window, Create a profile name with 'Firefox6.0.2'
4. Repeat step 3 for all firefox versions, create unique profile for each version
5. To run a specific version of firefox use below command:
<path to firefox executable> -no-remote -P <profile name>


C:\Program Files\Mozilla Firefox_6.0.2\firefox.exe -no-remote -P Firefox6.0.2
C:\Program Files\Mozilla Firefox_7.0.1\firefox.exe -no-remote -P Firefox7.0.1

About url in firefox

There are few special URLs which begins with about: that you can type into the firefox location bar:

about: => The same page as Help -> About
about:blank => A blank page
about:cache => Displays cache statistics and directory location
about:config => GUI for modifying user preferences
about:plugins => List all plugins
about:logo => Displays the firefox logo

There is an extension available for firefox to save advanced preferences. gui:config makes it easier to change preferences that can only be found in the “about:config”. This add on can be downloaded from https://addons.mozilla.org/en-US/firefox/addon/5523