Having Firefox 4 RC released with Tab Management feature (Panorama) and supports latest technologies and web standards, if you’ve installed Firefox 4 RC/final over existing installed Firefox 3.6 version in your Computer you’ll be automatically upgraded to Firefox 4. If you want to revert back to Firefox 3.6 which is called downgrading, here is how to downgrade from Firefox 4 to Firefox 3.6 or earlier versions.
Why should I downgrade? one major reason is extensions worked in Firefox 3.6 may not be compatible with latest Firefox 4 version. No one wants to sacrifice his favorite extensions, if you’re one of those this article will be for you.
Downgrading from Firefox 4 to Firefox 3.6 or earlier versions
1. Visit Mozilla FTP Server in your browser.
2. Open latest Firefox 3.6 version folder (currently Firefox 3.6.15)
3. Open “Win32” folder and further open “en-US“ folder.
4. Download Firefox setup and install in your Computer, you’ll be automatically downgraded to Firefox 3.6. x version.
To downgrade to Firefox 3.5.x version, you can download and install latest version from here by choosing your Operating System and language.
If you want to use or stay on Firefox 3.6.x/3.5.x version forever disable update for Firefox from Tools>Options>Advanced>Update uncheck for Firefox under “Automatically check for Updates to”.