@namespace url(http://www.w3.org/1999/xhtml);

@-moz-document url("http://www.bbc.co.uk/cbbc/smile/games/jambusters/jambusters_popup.shtml") {
  body {
    background-color:#000000;
  }
  #jambusters {
    display:block;
    margin:0 auto;
  }
}