<html>
<head>
</head>
<body>
<p style="text-align:center"><input type="button" value="Masquer" id="btn"> </p>
<div id="zone" style="background-color:#F90; height:30px; width:500px; margin:auto; text-align:center; display:block">Zone visible ou masquée</div>
</body>
</html>