Install Firefox 4 Beta alongside Firefox 3.6?
I am doing web development and I have Firefox 4 and I need to test in Firefox 3.6 with Firebug. Can I install both Firefox 4 and Firefox 3.6?
You can run different versions of Firefox, (among other apps) in your browser, without downloading them, using Spoon. Give it a try...
Note: I am not affiliated with this product in any way, shape, or form.
You don't have to install both Firefox 4 and Firefox 3.6. Get the portable version for the release you need: http://portableapps.com/apps/internet/firefox_portable/localization
There are more complicated solutions using the Profile Manager, but running a portable version is much faster.