html { 
  background:url(images/4click.png) no-repeat center center fixed; 
  background-size: 100VW 100VH;
}

body{
    height: 100%;
}

a:link, a:visited {
    position: absolute;
    background-color:transparent;
    color: white;   
    bottom:10vh;
    left: 30vw;
    height: 110px;
    width: 600px;
    text-decoration: none;
    display: inline-block;
}