.content {
  position: absolute;
  left: 50%;
  top: 50%;
  border-style:solid;
  z-index:1000;
  padding:5px;
  border-radius:10px;
  background-image: url('https://geocities.ws/e-paper/images/b1.jpg');
  background-size: contain;
  -webkit-transform: translate(-50%, -50%);
  transform: translate(-50%, -50%);
}