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

@-moz-document url-prefix("http://video.google.com/videoplay?docid=") {

body {
opacity: 0.0 !important;
background: #000 !important;
}

body:hover {
opacity: 1.0 !important;
background: #fff !important;
}

}