<html>
<body>
<script language="JavaScript">
function function1() {
var m = screen.logicalXDPI;
var n = screen.logicalYDPI;
alert("Screen XDPI =\n"+m);
alert("Screen YDPI =\n"+n);
}
</script>
<input type="button" value="Click me" onclick="function1();">
</body>
</html>