html,
body{
 height: 100%;
}

#cover {

  background: url('../img/homepage.gif') no-repeat center center fixed;
  -webkit-background-size: cover;
  -moz-background-size: cover;
  background-size: cover;
  -o-background-size: cover;
  background-size: cover;
  height: 100%;
  text-align: center;
  display: flex;
  align-items: center;
}

#cover2 {

  background: url() no-repeat center center fixed;
  -webkit-background-size: cover;
  -moz-background-size: cover;
  background-size: cover;
  -o-background-size: cover;
  background-size: cover;
  background-color: black;
  height: 100%;
  text-align: center;
  display: flex;
  align-items: center;
}

#cover-caption {
  width: 100%;
}