diff --git a/functions/http.xml b/functions/http.xml
index 7afa59d841..be3f523c41 100644
--- a/functions/http.xml
+++ b/functions/http.xml
@@ -1,5 +1,5 @@
 <?xml encoding="iso-8859-1"?>
-<!-- $Revision: 1.26 $ -->
+<!-- $Revision: 1.27 $ -->
  <reference id="ref.http">
   <title>HTTP functions</title>
   <titleabbrev>HTTP</titleabbrev>
@@ -60,6 +60,24 @@ exit;                 /* Make sure that code below does
       </programlisting>
      </informalexample>
     </para>
+    <note>
+     <para>
+      HTTP 1.1 requires an absolute URI as argument to 
+      <ulink url="&spec.http1.1;/rfc2616-sec14.html#sec14.30">Location:</ulink>
+      including protocol, hostname and absolute path. Some clients
+      might accept relative URIs but you definetly should not rely on
+      it. You can usually use $HTTP_SERVER_VARS['HTTP_HOST'],
+      $HTTP_SERVER_VARS['PHP_SELF'] and <function>dirname</function>
+      to make an absolute URI from a relative one yourself:
+      <informalexample>
+       <programlisting>
+Header ("Location: http://".$HTTP_SERVER_VARS['HTTP_HOST']
+                       ."/".dirname($HTTP_SERVER_VARS['PHP_SELF']
+                       ."/".$relative_url);
+       </programlisting>
+      </informalexample>
+     </para>
+    </note>
     <para>
      The second special-case is any header that starts with the
      string, &quot;HTTP/&quot; (case is not significant).  For