Remove empty space above tabs in Firefox 4 beta 6 title bar

These instructions for Firefox 4 beta 5/6.

1. Find your userChrome folder inside your Profile folder: to find your profile folder, see: http://kb.mozillazine.org/Profile_folder
   
   
2. Find the "chrome" folder and open it.
   
   
3. Edit userChrome.css
   
   
4. Add this snippet to that file:
   

   @namespace url(http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul);
   
   /* Note: assumes app button is visible (menu bar disabled) */
   
   /* Move tabs up to titlebar */
   #main-window[sizemode="maximized"] #navigator-toolbox[tabsontop="true"] #TabsToolbar {
       padding-left: 112px !important;
       padding-right: 112px !important;
   }
   #main-window[sizemode="normal"] #navigator-toolbox[tabsontop="true"] #TabsToolbar {
       padding-left: 112px !important;
       padding-right: 109px !important;
   }
   
   /* Move the menubar above the tabs so it moves the tab bar down when activated */
   #main-window[sizemode="maximized"] #navigator-toolbox[tabsontop="true"] #toolbar-menubar {
       margin: -19px 0px 3px 112px !important;
   }
   #main-window[sizemode="normal"] #navigator-toolbox[tabsontop="true"] #toolbar-menubar {
       margin: -24px 0px 3px 112px !important;
   }
   
   /* Curved corners when tabs-on-top and normal window */
   #main-window[sizemode="normal"] #navigator-toolbox[tabsontop="true"] #nav-bar {
       -moz-border-radius-topleft: 5px !important;
       -moz-border-radius-topright: 5px !important;
   }
   

   (taken from http://userstyles.org/styles/36432)
   
   
5. Restart Firefox.