Demo

Div avec id="content"

<style>
* {
	font-family: "Trebuchet MS", Arial, Helvetica, sans-serif;
	font-size: 12px;
}

body {
	margin: 30px 0;
	padding: 0;
	background: #EFEFEF;
	font-size: 12px;
	color: #6B6B6B;
	text-align:center;

}

#top {
	background: url(http://jc.pix.free.fr/web/borders/rounded-width917/top.gif) no-repeat;
	margin: 0 auto;
	float: center;
	padding: 0 0 0 0;
	width: 917px;
	height: 12px;
}

#content {
	width: 917px;
	text-align: left;
	margin: 0 auto;
	background: url(http://jc.pix.free.fr/web/borders/rounded-width917/content.gif);
}

#spacer {
	padding: 0 30 0 30;
}

#footer {
	background: url(http://jc.pix.free.fr/web/borders/rounded-width917/footer.gif) no-repeat;
	margin: 0 auto;
	padding-top: 10px;
	width: 917px;
}
</style>