diff --git a/doc/config.html b/doc/config.html
index fe601068..02cdc8f7 100755
--- a/doc/config.html
+++ b/doc/config.html
@@ -1566,7 +1566,9 @@ ID display = TAG-$message id
         attributes, which are used for sorting. The first attribute in the list
         has the highest priority. Only if two entries have the same value in
         the first sort attribute, they are sorted according to the second sort
-        attribute and so on.
+        attribute and so on. The list of attributes may contain <b>ID</b> and
+        <b>logbook</b>, although <b>ID</b> makes only sense together with
+        other attributes.
       </li>
     </ul><a name="conditional" id="conditional"></a>
     <hr>