jQuery UI overlay not showing?

all. I am trying to get an overlay to work on my Modal box.

How can I create a working overlay?

I am using jQuery UI and have got it to work apart from the overlay.

Here is the code to call the module:

function showDialog(){
    $("#example").dia开发者_如何学Pythonlog();
    return false;   
}

$(window).resize(function() {
    $("#example").dialog("center", "center", "center");
});

How can I call an overlay?

If you click the link Show the Dialog in the url below:

http://satbulsara.com/NSJ-LOCAL-02-06/eqs1.htm

Thanks,

Sat

---

To make a dialog modal, all you have to do is specify true for the modal option:

function showDialog(){
    $("#example").dialog({
        modal: true // Make the dialog "modal" (show an overlay beneath the dialog)
    });
    return false;   
}

Here's an example on jQueryUI's website.