Ok. I am a little dense. What I want is:

if there is a detailed page, to link to that
if there is a URL, to link to that
if there is not a url or a detailed page, to just show the title, not linked.

What I have so far, that does the first two, is this:

<%if Full_Story%><a href="<%detailed_url%>"><%body_font%><b><%Title%></b></font></a>
<%else%><a href="<%db_cgi_url%>/jump.cgi?ID=<%ID%>"><%body_font%><b><%Title%></b></font></a>
<%endif%>

Can you show me using this example, how to add the <%if not URL%>?

I am not trying to be difficult. I swear.