<html>
	<head>
		<title>Centrage vertical</title>
<style>
		    height:500px;
     width:700px;
     position: relative;
 }
 #temp {
     position:absolute;
     height:1px;
     overflow: visible;
     top:50%
 }
 #content {
     position:absolute;
     height:200px;
     width:200px;
     top:-100px;
 }
</style>
	</head>
	<body>
<div id="container">
   <div id="temp">
     <div id="content">
       Contenu du div à centrer
     </div>
   </div>
 </div>
	</body>
</html>