Though I'm too late, but this is very easy and simple. Page center is always left 50%, and top 50%. So minus the div width and height 50% and set left margin and right margin. Hope it work's for everywhere -
body{
background: #EEE;
}
.center-div{
position: absolute;
width: 200px;
height: 60px;
left: 50%;
margin-left: -100px;
top: 50%;
margin-top: -30px;
background: #CCC;
color: #000;
text-align: center;
}
This is center div