Ho trovato questo ma legge solo i dati dal mio sito, magari qualcuno sa come adattarlo per specificare un url esterno?

codice:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>

<head>
<meta name="description" content="Tutorials from www.vogella.de!"> 

<script type="text/javascript">
function getMetaDescription () {
  var metaElements = document.all ?
    document.all.tags('META') :
    document.getElementsByTagName ?
    document.getElementsByTagName ('META') : new Array();
  var metaKeywords = new Array();
  var i = 0;
  for (var m = 0; m < metaElements.length; m++)
    if (metaElements[m].name == 'description')
      metaKeywords[i++] = metaElements[m].content;
  return metaKeywords;
}
</script>
</head>

<h2>
This will write the meta tag description to this page
</h2>

<body>

<script type="text/javascript">
	document.write(getMetaDescription());
</script>


</body>
</html>