Yes, you can. Could you mention a few things you don't like? Things like the orange Firefox button vs. menus, tabs on top vs. where they were before, etc., are all changeable. But maybe you have run into some other problems. Feedback is helpful. --- To rollback to 3.6: First, make a backup of your computer for safekeeping. To back up Firefox, see [https://support.mozilla.com/en-US/kb/Backing+up+your+information Backing up your information]. Next, download and save Firefox 3.6 to your desktop for future installation. http://www.mozilla.com/firefox/all-older Close Firefox 4, and uninstall it. Do not remove your personal data and settings, just the program. Then finally you can reinstall Firefox 3.6. Unless you have installed an incompatible add-on, it should pick up where you left off. If there are serious issues, please post back with details. Note: I haven't actually tried this myself!