body{
position: relative;
width: 100%;
height: 100%;
}
div{
position:absolute;
width:400px;
height:400px;
left:50%;
top:50%;
margin:-200px 0 0 -200px;
}
body{
position: relative;
width: 100%;
height: 100%;
}
div{
position:absolute;
width:400px;
height:400px;
left:50%;
top:50%;
margin:-200px 0 0 -200px;
}