CodingForums.com - javascript Iframe PopUp help

Hi, I am making an Iframe to pop up when users is leaving a page.. It is like a goodbye message. Now i have called a function with window.onbeforeunload.

The problem is that the iframe fires but disappears quickly.

To be precise it is a MOOdle popup and below is the code.

Code:

<html>

<head>

<title></title>



<script type="text/javascript" src="javascript/moodalbox121compressed/js/mootools.js"></script>

<script type="text/javascript" src="javascript/moodalbox121compressed/js/moodalbox.js"></script>

<script type="text/javascript" src="javascript/modalbox.js"></script>

<link href="javascript/moodalbox121compressed/css/moodalbox.css" rel="stylesheet" type="text/css" media="screen">

<script type="text/javascript">

window.onbeforeunload = popup;

function popup(){

MOOdalBox.open( "popup.htm","Some kind of caption", "450 305" )



}</script>



</head>