jQuery.fn.center = function () {
    this.css("position", "fixed");
    this.css("top", (($(window).height() - this.outerHeight()) / 2) + $(window).scrollTop() + "px");
    this.css("left", (($(window).width() - this.outerWidth()) / 2) + $(window).scrollLeft() + "px");
    return this;
}

$(function () {
    $('.modal-dialog').center();
    /* $('.modal-dialog').dialog({
    closeOnEscape: false,
    draggable: false,
    modal: true,
    resizable: false,
    title: 'Please provide your name, email and DOB.',
    width: 500,
    height: 350
    }
    );*/

    $(window).resize(function () { $('.modal-dialog').center(); });

});