Admin/page/dist-layout/navigation.html

Removed theory NatDef.

<p>
&nbsp;
<center>
<a href="index.html"><img src="isabelle.gif" width="100" height="86" alt="[Isabelle logo]" border="0"></a>
</center>
<p>
<center>
<strong>Isabelle Distribution Area</strong>
</center>
&nbsp;
<p>
<!-- _GP_ setnavcolor("#F0F0F0") -->
<!-- _GP_ page("Mirrors", "index") -->
<!-- _GP_ empty_line(3) -->
<!-- _GP_ page("Packages", "packages") -->
<!-- _GP_ empty_line(3) -->
<!-- _GP_ page("Documentation", "docs") -->
<!-- _GP_ empty_line(3) -->
<!-- _GP_ page("Past Releases", "past") -->
<!-- _GP_ empty_line(3) -->
&nbsp;
&nbsp;