html, body {
height: 100%;
margin: 0;
padding: 0;
}
img#bg {
position:fixed;
top:0;
left:0;
width:100%;
height:100%;
}

#center {
  position:relative;
  z-index:1;
  top: 80%;
  width: 230px;
  height: 31px;
  left: 15%;
}