Slight rewording.

web/templates/default/lastcallers.inc

@@ -5,7 +5,7 @@
     <td class="main" valign="top"><br />
 
 
-<h3 align="center">Last Few Callers to @@system:name@@</h3>
+<h3 align="center">Last Few Callers on @@system:name@@</h3>
 <table class="lastcallers">
     <tr><td><pre class="leftalign">@@lastcallers@@</pre></td></tr>
 </table>