gecko/image/test/reftest/gif/ImageDocument.css

body {
  background: #222 url(noise.png);
  margin: 0;
}

body > :first-child {
  display: block;
  position: absolute;
  margin: auto;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  background-color: #fff;
  color: #222;
}