$(document).ready(function () {
  
    $("a[rel=img_group]").fancybox({
        transitionIn: "fade",
        transitionOut: "fade",
        titlePosition: "over",
        titleFormat: function (a, b, c, d) {
            return '<span id="fancybox-title-over" style="color: #ffffff;">' + a + "</span>"
        }
    });

});