Salve, io dovrei limitare l'are del drag e drop di questo script

Codice PHP:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Untitled Document</title>
<script src="prototype.js" type="text/javascript"></script>
<script src="scriptaculous.js" type="text/javascript"></script>
<script type="text/javascript">
/* <![CDATA[ */
function salva() {
    var elemento = document.getElementById("profilo");
    alert("X: " + elemento.style.left + " | Y: " + elemento.style.top);
}
/* ]]> */
</script>
<script type="text/javascript">
// Take all the elements whatever you want to make Draggable.
   var elements = [
   'profilo'
   ];
// Make all the items drag able by creating Draggable objects
window.onload = function() {
   elements.each(
       function(item) {
           new Draggable(item, {container: 'main'});
       }
   );
}
</script>
</head>
<body>
<div id="main" style="background-color:#0CF" width="300" height="300">
<div id="profilo" style="background-image:url(../loghi/logo.png); width:100px; height:100px;"></div>







</div>
<input type="button" name="button1" value="Mostro Coordinate" onclick="salva()" />
</body>
</html>