body{
margin:0;
padding:0;
text-align:center;
background-color:#999;
}
#mainContainer {
position: absolute;
top:50%;
right:0;
bottom:0;
left:0;
width:100%;
height:600;
margin-top:-300px;
}
#contentContainer{
margin-left:auto;
margin-right:auto;
margin-top:0px;
width:100%;
height:600px;
}
#flashContainer {
margin-left:auto;
margin-right:auto;
margin-top:30px;
width:950px;
height:600px;
background-color:#444;
padding:10px;
}