Close the Browser forcefully using javascript

<HTML>
<head>
<script language="JavaScript">
//window.onbeforeunload = confirmExit(); // close on befor load
function confirmExit()
{
window.close();
}
</script>
</head>
<body>
<input type="button" id="B1" value="Test" onclick="javascript:confirmExit();">
</body>
</HTML>