Dear Walter Howard,
Because I changed the code in the yt plugin before, your site was normal with the site offline.
Please go to "plugins\system\yt\yt.php", finding:
$uri = str_replace(J_SEPARATOR, "/", str_replace(JPATH_SITE, JURI::base(), dirname(__FILE__)));
$uri = str_replace(DIRECTORY_SEPARATOR , '/', str_replace("/administrator/", "", $uri));
$html = "";
if(J_VERSION=='2'){
$html .= '<script language="javascript" type="text/javascript" src="'.$uri.'/includes/assets/jquery.min.js"></script>';
$html .= '<script language="javascript" type="text/javascript" src="'.$uri.'/includes/assets/jquery-noconflict.js"></script>';
}
=>
$uri = str_replace(J_SEPARATOR, "/", str_replace(JPATH_SITE, JURI::base(), dirname(__FILE__)));
$uri = str_replace(DIRECTORY_SEPARATOR , '/', str_replace("/administrator/", "", $uri));
$html = "";
Thanks