Georgi said:
It is possible but I strictly recommend you to not use this feature.
You can simply
atach alert function to onunload event handler on BODY tag for example.
<script type="text/javascript">
function myReminder(){
alert("Do you save the changes?");
}
</script>
</head>
<body onunload="myReminder();">
But it is very irritatingli for some users and not good decision about
crossbrowser compatibility.
and also very annoying when it gets used for asking you if you want to
bookmark (or set as home pg on browser) the url you're leaving... in
this case I think it would be more justified, maybe do it so users get
reminded only the first few times they visit (can this be done just
client-side? don't remember now...)