In your popup() function you are referncing images.image_ID. This will come over as "images.image_ID", and not translate to the id.
You could change your popup to pass in the ID that you want.
<script Language="JavaScript">
function popup(id)
{
settings="toolbar=yes,location=yes,directories=yes,"+
"status=no,menubar=no,scrollbars=yes,"+
"resizable=yes";
MyNewWindow = window.open("full_img.cfm?toshow=" + id);
}
</script>
Then in your HTML/CFML code
<!--- Display images associated with article--->
<cfoutput query= "myQuery2">
<a href="" onClick="popup(#myQuery2.image_ID#);">
<img src="#myquery2.image_thumbpath#" alt="image thumbnail">
</a>
</cfoutput>
I know you are teaching yourself ColdFusion. I'd recommend you use the cfqueryparam tag in your queries to protect against SQL attacks. You would need to use it around your #URL.ID# in your queries.
So this:
...WHERE articles.article_ID = #URL.ID#
would be this:
...WHERE articles.article_ID = <cfqueryparam value = "#URL.ID#" cfsqltype = "cf_sql_integer">
Hope that helps some.