function saveChanges(obj){
    var success    = function(t){editComplete(t, obj);}
    var failure    = function(t){editFailed(t, obj);}

    // pars = Form.serialize("menu_plugin_form");

    var url = '{site_url}/site/menu.php?mode=save';
    var forum = $F("forum");
    var forumcheckbox = $F("checkbox_forum");
    var pars = Form.serialize("menu_plugin_form");
    
    var myAjax = new Ajax.Request(url, {method:'post', postBody:pars, onSuccess:success, onFailure:failure});
}

function editComplete(t, obj){
    obj.innerHTML    = t.responseText;
}

function editFailed(t, obj){
    obj.innerHTML    = 'Sorry, the update failed.';
}