$.maxZIndex = $.fn.maxZIndex = function (opt) {
    var def = { inc: 10, group: "*" };
    $.extend(def, opt);
    var zmax = 0;
    $(def.group).each(function () {
        var cur = parseInt($(this).css('z-index'));
        zmax = cur > zmax ? cur : zmax;
    });
    if (!this.jquery)
        return zmax;

    return this.each(function () {
        zmax += def.inc;
        $(this).css("z-index", zmax);
    });
}