$(function() {
    $( "#sortable" ).sortable({
        update : function () {
            $( "#log" ).load("/wp-admin/admin-ajax.php");
            var serial = $( "#sortable" ).sortable('serialize');
            alert(serial);
            $.ajax({
                url: "/wp-admin/admin-ajax.php",
                type: "post",
                data:  {action: 'MyAjaxFunction', serial: serial,},
                error: function(){
                    alert("theres an error with AJAX");
                },
                success: function(){
                    alert("AJAX SUCCESS");
                }
            });
        }
    });
    $( "#sortable" ).disableSelection();
});