html, body {margin: 0; padding: 0; height: 100%;}
body {margin:0 auto 0 auto;}

#wrap {
position: relative;
width: 850px;
height: 100%;
margin: 0 auto;
}

#containercentre {
position: absolute;
top: 50%;
left: 50%;
height: 600px;
margin-top: -300px;
width: 850px;
margin-left: -425px;
}