You should add/replace this in the content.func.inc.php file at the last lines (around 393):
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Code below makes also the description meta working!!
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// add possible redirection code (article summary) to $block["htmlhead"];
$block["htmlhead"] = $content["redirect"]["code"].$block["htmlhead"]."\n";
// insert description meta tag if not definied
if(!stristr($block["htmlhead"], '"description"') && $content["articles"][$aktion[1]]["article_summary"]) {
$block["htmlhead"] .= '<meta name="description" content="';
$block["htmlhead"] .= html_specialchars($content["articles"][$aktion[1]]["article_summary"])."\">\n";
}
// insert keywords meta tag if not definied
if(!stristr($block["htmlhead"], '"keywords"') && $content["articles"][$aktion[1]]["article_keyword"]) {
$block["htmlhead"] .= '<meta name="keywords" content="';
$block["htmlhead"] .= html_specialchars($content["articles"][$aktion[1]]["article_keyword"])."\">\n";
}
// insert author meta tag name
$block["htmlhead"] .= '<meta name="author" content="';
$block["htmlhead"] .= html_specialchars($content["articles"][$aktion[1]]["article_username"])."\">\n";
$block["htmlhead"] .= '<meta name="publisher" content="
www.tuinenvijver.nl">
<meta name="robots" content="all">
<meta name="revisit-after" content="2 weeks">
<meta name="Rating" content="General">
<meta name="Language" content="nl">
<meta name="Generator" content="
http://www.added-value.nl">
<meta name="distribution" content="Global">
<meta name="Copyright" content="2004 Tuin en Vijver">';