protected void Page_Load(object sender, EventArgs e)
        {
            // get the page navigation id
            if (!int.TryParse(Request.QueryString["InstanceId"], out _instanceId))
            {
                _instanceId = WebModulesProfile.Current.StartPageId;

                if (_instanceId <= 0)
                {
                    _instanceId = Webpage.RootNavigationId;
                }
            }

            if (!IsPostBack)
            {
                //check user permissions.
                if (!NavigationRole.IsUserAuthorized(_instanceId, Page.User))
                {
                    throw new System.Security.SecurityException(Permission.MSG_SECURITY_FAILURE);
                }

                bool allowEdit       = Permission.AllowEditContent();
                bool allowManagePage = Permission.AllowManagePage();

                //sort buttons
                ModulesGridView.Columns[3].Visible = allowEdit;
                ModulesGridView.Columns[4].Visible = allowEdit;
                //settings
                ModulesGridView.Columns[5].Visible = allowEdit;
                //delete
                ModulesGridView.Columns[6].Visible = allowManagePage;

                LoadModules();
            }
        }