body {
  background-color: #88bef5;
  background-image: url("https://78.media.tumblr.com/15f2cf74f396b95b2fc7788ed744b10f/tumblr_pd1njbn8BB1rqnly5_540.gif");
  background-attachment: scroll;
  background-size: cover;
}
div {
  margin: auto;
  width: 50%;
  padding: 20px;
}

https://i.imgur.com/3ciD9.gif