codice:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title></title>
<style type="text/css">
#im:hover {background:url('img.jpg');}
#im {background: url('img.gif');width:500px;height:300px;}
</style>
</head>

<body>
<div id="im">&nbsp;</div>
</body>
</html>