html {
width: 100%;
height: 100%;
background-color: #525154;
}

body {
margin: 0;
padding: 0;
width: 100%;
height: 100%;
}

#placeholder-img {
position: absolute;
width: 800px;
height: 640px;
background-image: url(bg.jpg);
left: 50%;
top: 50%;
margin-left: -400px;
margin-top: -320px;
}