html, body {
  margin: 0;
  padding: 0;
  background: url(../img/image.jpeg) no-repeat center center fixed; 
  -webkit-background-size: cover;
  -moz-background-size: cover;
  -o-background-size: cover;
  background-size: cover;
}

.background_ {
  position: absolute;
  display: block;
  top: 0;
  left: 0;
  z-index: 0;
}