codice:
<!DOCTYPE html>
<html>


<head>


<style type="text/css">
div#contenitore { width:697px; height:1387px; padding:0;  }
img#jpg { position:absolute; z-index:1; width:697px; height:1387px; }
img#gif { position:relative; z-index:2; top:50%; left:50%; margin-top:-156px; margin-left:-156px; width:312px; height:312px; }
</style>
</head>


<body>
<div id="contenitore">
<img src="http://imagizer.imageshack.us/v2/640x480q90/924/u2Hsct.jpg" id="jpg" >
<img src="http://imagizer.imageshack.us/a/img923/4737/IfPFnP.gif" id="gif" >
</div>


</body>


</html>