/* GENERAL CSS DOCUMENT */

body {
	color:#000;
	background:#f5f5f5;
	font-family:"Helvetica Neue", Arial, Helvetica, sans-serif;
}

div#background {					
	position: absolute;
	background: #CCC;
	width: 960px;		/* reduced to account for padding */	
	height: 100%;
	top: 30px;
	left: 50%;			/* DIV-BASED CENTERING PART 1 */
	margin-left:-490px;	/* DIV-BASED CENTERING PART 2 */
	padding: 10px;		/* enforces distance between DIV edge and contents */
}
	
div#container {
	position: relative;
	background:#f5f5f5;	
	height: 80px;		/* decreased to account for XXX */
	width: 80px;		/* decreased to account for XXX */
	margin: 10px;		/* positions DIV relative to parent container, does not affect actual size */
	padding: 10px;		/* positions DIV contents relative to interior border, does affect actual size */
	/* border: 1px solid black; borders also affect actual size, test by uncommenting*/
	float: left;
	}
	
/* note how the final position is a mix of background padding and plainbox padding */

General CSS Document

CSS