The pageY property of the Event object controls the vertical (y-coordinate) positioning.
<html>
<head>
<title>Example of the event.pageY property</title>
</head>
<body>
<script language = "JavaScript">
<!-- function handle(evnt){
alert("The Y coordinate of where the click event occurred is: " + evnt.pageY); return true;
}
window.onclick = handle;
-->
</script>
Click in the web browser.
</body>
</html>