gistfile1.js

(function ($) {
    $.fn.center = function () {
        return this.each(function () {
            var top = ($(window).height() - $(this).outerHeight()) / 2;
            var left = ($(window).width() - $(this).outerWidth()) / 2;
            $(this).css({
                position: 'absolute',
                margin: 0,
                top: (top > 0 ? top : 0) + 'px',
                left: (left > 0 ? left : 0) + 'px'
            });
        });
    };
})(jQuery);