html, body {
  margin: 0;
  padding: 0;
  height: 100%;
  overflow: hidden;
  background: #000;
}

#contentIFrame {
  border: none;
  position: absolute;
  top: 50%;
  left: 50%;
  transform-origin: top left;
}

#dummyIFrame {
  display: none;
}