如何在关闭窗口时提示

例子：<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><html>
<head>
<title>Untitled</title>
<Script language="Javascript">
<!--
var bReload = 0;

function reload(){
bReload = 1;
}

function close(){
if (bReload == 0){
alert('to be Closed.');
}
}
//-->
</Script></head><body onunload="javascript:close();" onbeforedeactivate="javascript:reload()">Hello World!</body>
</html>测试环境：
Win2000 ， IE6 + SP2