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;