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

#toggleSidebarAutohide {
  -moz-appearance: none !important;
  width: 24px !important;
  height: 24px !important;
  background-image: url(chrome://moztweaks/skin/tweaksEnabled.png) !important;
  background-position: center !important;
}

#toggleSidebarAutohide[checked="true"] {
  -moz-appearance: none !important;
  background-image: url(chrome://moztweaks/skin/tweaksDisabled.png) !important;
}