For those of you looking for a way to absolutely center align a DIV using CSS only, and want to retain its fluidity, please see the following code:

#container {
position: absolute;
left: 50%;
top: 50%;
width:560px;
height:380px;
margin-left: -280px; /* MUST UPDATE TO MATCH HALF THE WIDTH */
margin-top: -190px;  /* MUST UPDATE TO MATCH HALF THE HEIGHT */
}