On close pop up window alert message

Question

How to make when I open pop up window and close to say message Want close... this code work on main page but I need to close external page... What I need to fix in this code. Thanks...

<script>
    function openwindow(){
        window.open("http://www.google.com","mywindow","menubar=1,resizable=1,width=550,height=550");
    }
    </script>

    <p>
    <A href="javascript: openwindow()">Open Window</A>
    </p>

    <script type="text/javascript">
    window.onbeforeunload = function () {
        return "Want Close?";
    }
    </script>

Answer 1

You can't make this work.

When the user opens a new window, you basically don't have control over it, instead you host it ( can modify the content ) on your own.