#main-div {

position: absolute;
top: 50%;
left: 50%;
width: 60em;
height: 54em;
margin-top: -27em; /*always take 1/2 from the size of the height, they have to be negative*/;
margin-left: -30em; /*always take 1/2 from the size of the width, they have to be negative*/
text-align: left







}