html { 
  background: url(STScI-01G7DB1FHPMJCCY59CQGZC1YJQ.png) no-repeat center center fixed; 
  -webkit-background-size: cover;
  -moz-background-size: cover;
  -o-background-size: cover;
  background-size: cover;
}

body {
    margin: 0;
    color: rgb(255,255,255);        /* white */
}