<script src="//ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.js"></script>

<script>
$(document).ready(function() {

var id = '#dialog';

//Get the screen height and width
var maskHeight = $(document).height();
var maskWidth = $(window).width();

//Set heigth and width to mask to fill up the whole screen
$('#mask').css({'width':maskWidth,'height':maskHeight});

//transition effect
$('#mask').show(1000);
$('#mask').fadeTo("slow",0.5);

//Get the window height and width
var winH = $(window).height();
var winW = $(window).width();

//Set the popup window to center
$(id).css('top',  winH/2-$(id).height()/2);
$(id).css('left', winW/2-$(id).width()/2);

//transition effect
$(id).show(2000);

//if close button is clicked
$('.window .close').click(function (e) {
//Cancel the link behavior
e.preventDefault();

$('#mask').hide();
$('.window').hide();
});


//if mask is clicked
$('#mask').click(function () {
$(this).hide();
$('.window').hide();
});




});

</script>