Thanks, I've had a look again at that html file. I'm using the water_drop theme, can't see any reference to the description tag.
The code in template.html for the <head> section of the displayed page doesn't contain the meta tags for "robots", "keywords" or "description":
...
<head>
<meta http-equiv="Content-Type" content="text/html; charset={CHARSET}" />
<meta http-equiv="Pragma" content="no-cache" />
<title>{TITLE}</title>
{META}
<link rel="stylesheet" href="themes/water_drop/style.css" type="text/css" />
<script type="text/javascript" src="scripts.js"</script>
<!--
SVN version info:
Coppermine version: 1.4.19
$Revision: 4392 $
$LastChangedBy: gaugau "
$Date: 2008-04-16 09:25:35 +0200 (Mi, 16 Apr 2008) $
-->
</head>
...
Comparing this to the <head> section actually displayed (see below, sorry for the large post, thought it better not to snip out sections), it's becoming clearer to me that the CPG template.html is being merged into what I imagine is a Joomla "template" or equivalent. I had expected that the Bridge version of functions.inc.php (specifically the pageheader function) would be responsible but it doesn't appear to be so.
<head>
<meta http-equiv="content-type" content="text/html; charset=utf-8" />
<meta name="robots" content="index, follow" />
<meta name="keywords" content="space, coins, exonumia, medal, memorabilia, tokens" />
<meta name="description" content="www.spacecoins.net - coins, medals and other memorabilia of Man's greatest achievement." />
<meta name="generator" content="Joomla! 1.5 - Open Source Content Management" />
<link href="/templates/ja_purity/favicon.ico" rel="shortcut icon" type="image/x-icon" />
<script type="text/javascript" src="/media/system/js/mootools.js"></script>
<link rel="stylesheet" href="http://www.spacecoins.net/templates/system/css/system.css" type="text/css" />
<link rel="stylesheet" href="http://www.spacecoins.net/templates/system/css/general.css" type="text/css" />
<link rel="stylesheet" href="http://www.spacecoins.net/templates/ja_purity/css/template.css" type="text/css" />
<meta name="verify-v1" content="YnfNhg8EeWqw0/nLCOlomISCDVJHUj4/zQETfpKKIT0=" />
<script language="javascript" type="text/javascript" src="http://www.spacecoins.net/templates/ja_purity/js/ja.script.js"></script>
<script language="javascript" type="text/javascript">
var rightCollapseDefault='show';
var excludeModules='38';
</script>
<script language="javascript" type="text/javascript" src="http://www.spacecoins.net/templates/ja_purity/js/ja.rightcol.js"></script>
<link rel="stylesheet" href="http://www.spacecoins.net/templates/ja_purity/css/menu.css" type="text/css" />
<link rel="stylesheet" href="http://www.spacecoins.net/templates/ja_purity/styles/background/lighter/style.css" type="text/css" />
<link rel="stylesheet" href="http://www.spacecoins.net/templates/ja_purity/styles/elements/black/style.css" type="text/css" />
<!--[if gte IE 7.0]>
<style type="text/css">
.clearfix {display: inline-block;}
</style>
<![endif]-->
<style type="text/css">
#ja-header,#ja-mainnav,#ja-container,#ja-botsl,#ja-footer {width: 97%;margin: 0 auto;}
#ja-wrapper {min-width: 100%;}
</style>
<!-- +++++++++++++++++++ Script head +++++++++++++++++++ -->
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta http-equiv="Pragma" content="no-cache" />
<title>spacecoins.net Photo Gallery - Men in Space Series 2 (Danbury Mint)/First Lunar Exploration (Reverse)</title>
<meta name="keywords" content="kw_Apollo"/><link rel="start" href="displayimage.php?album=17&pos=0" title="Return to start" />
<link rel="last" href="displayimage.php?album=17&pos=12" title="Skip to end" />
<link rel="prev" href="displayimage.php?album=17&pos=5" title="See previous file" />
<link rel="next" href="displayimage.php?album=17&pos=7" title="See next file"/>
<link rel="up" href="thumbnails.php?album=17&page=1" title="Return to the thumbnail page"/>
<link rel="stylesheet" href="themes/water_drop/style.css" type="text/css" />
<script type="text/javascript" src="scripts.js"></script>
<!--
SVN version info:
Coppermine version: 1.4.19
$Revision: 4392 $
$LastChangedBy: gaugau $
$Date: 2008-04-16 09:25:35 +0200 (Mi, 16 Apr 2008) $
-->
</head>