You can change the layout so that it is like Firefox 3.6. For details see http://redherring2.wordpress.com/2011/01/17/firefox-4-restoring-firefox-3-ui In Firefox 4 by default the Stop, Go and Reload buttons are combined and attached to the right hand edge of the location bar. When you are typing in the location bar it will show the Go button. When a site is loading it shows the Stop button. At other times it shows the Reload button. If you want separate buttons, right-click on a toolbar and choose Customize, you can then drag and drop the stop or reload buttons and place them elsewhere. If you place them in the order "Reload-Stop" on the right hand edge of the location bar they will be combined again. For more details on customizing the toolbar see https://support.mozilla.com/kb/How+to+customize+the+toolbar ------ If you still want to downgrade to Firefox 3.6 first uninstall Firefox 4, but do not select the option to "Remove my Firefox personal data". If you select that option it will delete your bookmarks, passwords and other user data. You can then install the latest version of Firefox 3.6 available from http://www.mozilla.com/en-US/firefox/all-older.html - it will automatically use your current bookmarks, passwords etc. To avoid possible problems with downgrading, I recommend going to your profile folder and deleting the following files if they exist - extensions.cache, extensions.rdf, extensions.ini, extensions.sqlite and localstore.rdf. Deleting these files will force Firefox to rebuild the list of installed extensions, checking their compatibility, and reset toolbar customizations. For details of how to find your profile folder see https://support.mozilla.com/kb/Profiles