Edit in JSFiddle

$(document).ready(function() {
    $("#bloc").click(function() {
         $.blockUI({ message: $('#message'), css:{ width:512, height:384, cursor:'default' }});
    });
});

<button id="bloc">Block UI</button>
<div id="message" style="display: none;">
         <h1>Hello World!</h1>
    <script type="text/javascript">
        var init = false;
         $(document).ready(function () { alert("hello!");})
        init = true;
    </script>
</div>