Are you saying the icon is missing? Note: '''about:customizing''' is no longer present in Firefox 47+ releases. * Press '''Alt''' or '''F10''' to bring up the toolbar.<br>Then '''View > Toolbars > Customize. ''' * Right-click on a blank spot in the toolbar and<br>select '''Customize. ''' In the new window, look for the icon. When you find it, hold down the left button on it, and move it to where you want it to be. You can move any of the icons you want from here, but; '''some icons are locked in place. ''' There is also a '''Restore Defaults''' button at the bottom middle.