- For the latest Firefox browser version visit Mozilla Homepage.
- For old versions visit Old Apps.
1. Install Firefox 4 on C:\Program Files\Mozilla Firefox 4 (upon installation select "custom" to specify the directory when to install FF)
2. Install Firefox 3.x on C:\Program Files\Mozilla Firefox 3 (upon installation select "custom" to specify the directory when to install FF)
3. Create a desktop shortcut for both FF
4. Right-Click on Firefox 4 shortcut then click Properties
5. In the Shortcut Tab add this line to Target field -p PROFILE -no-remote
Example : "C:\Program Files\Mozilla Firefox 4\firefox.exe" -p PROFILE -no-remote6. Click OK
7. Double-Click on the Firefox 4 shortcut , then FF profile manager will appear
8. Create a profile for both FF3 and FF4 (see above).
Note: You'll probably only see one profile named "default." All you have to do is create a new profile for Firefox 3, but you may want to rename your existing profile to keep things tidy. I choose "Firefox3" and "Firefox4," ideally use a name with no space in it. Then click Exit
9. Again Right-Click on Firefox 4 shortcut then click Properties.
10. In the Shortcut Tab replace again Target field -p PROFILE -no-remote with -p Firefox4 -no-remote.
Example: "C:\Program Files\Mozilla Firefox 4\firefox.exe" -p Firefox4 -no-remote
11. Do Step 10 to other Firefox 3 shortcut but with -p Firefox3 -no-remote
Example: "C:\Program Files\Mozilla Firefox 3\firefox.exe" -p Firefox3 -no-remote12. There you go, FF3.x and FF4 browsers in your machine.