internal bool BackClicked()
        {
            if (!active || pos < 1)
            {
                return(false);
            }
            pos--;
            PageVisit p = (PageVisit)history [pos];

            ignoring = true;
            p.Go();
            ignoring              = false;
            backButton.Enabled    = pos > 0;
            forwardButton.Enabled = true;
            return(true);
        }