private function normalizeFolders($path = null)
    {
        $page = Page::html();
        $dir = $this->folder.'content/';
        // normalize
        if ($path && preg_match('/[^'.$page->url['chars'].'\/]/', $path)) {
            $seo = $this->url($path, 'slashes');
            if (is_dir($dir.$path)) {
                rename($dir.$path, $dir.$seo);
            }
            $path = $seo;
        }
        // folders
        foreach (glob($page->dir($dir, $path).'*', GLOB_ONLYDIR) as $folder) {
            $this->normalizeFolders(substr($folder, strlen($dir)));
        }
    }