Download the following file via FTP and open it in any text editor (/libraries/joomla/document/html/renderer/head.php)
find
$strHtml .= $tab.’<meta name=”generator” content=”‘.$document->getGenerator().’” />’.$lnEnd;
Add two slashes at the beginning of this code
//$strHtml .= $tab.’<meta name=”generator” content=”‘.$document->getGenerator().’” />’.$lnEnd;