@namespace url(http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul);

Autohide Menubar

menu {
  display: none !important;
}

#toolbar-menubar {
  height: 1px !important;
  min-height: 1px !important;
  overflow: hidden !important;
}

#toolbar-menubar:hover,
#toolbar-menubar:focus,
#toolbar-menubar:active {
  height: auto !important;
}

#navigator-toolbox > #toolbar-menubar {
  border-style: none !important;
}

#navigator-toolbox > #nav-bar {
  border-top: 0px !important;
}