I need this popup to show only once for each visitor. When the user clicks the close button the cookie should trigger and set the popup to not show for 30 days. I have tried installing a cookie myself, but to no avail as I have limited understanding of JavaScript. I've read several posts on here relating to this, but they id not help me.

JavaScript:

<link rel=stylesheet href=jquery-ui-1.10.3.custom/jquery-ui-1.10.3.custom.css />

<script src=http://code.jquery.com/jquery-1.9.1.js></script>

<script src=http://code.jquery.com/ui/1.10.3/jquery-ui.js></script>

<script>

$(function() {

$( #dialog-modal ).dialog({

height: 380,

width: 500,

modal: true,

buttons: {

    Ok: function() {

        $( this ).dialog( close );

        }

    }

});

});

</script>

HTML:

<div id=dialog-modal title=Please Note: class=content-list>

    <p>If you are taking advantage of our 21 day risk free trial <strong>your credit card will not be charged for 21 days</strong> after you receive your new biofeedback headband.</p>

    <ul>

        <li>Only Available for residents of the USA</li>

        <li>No Risk - 100% Money-Back Guarantee</li>

        <li>If you’re not satisfied we even pay for your return shipping</li>

    </ul>

</div>

Thanks.