add unknown session error

Author: christian-bromann

index.html

@@ -1334,6 +1334,14 @@ <h3>Errors</h3>
    but did not match an method for that URL.
  </tr>
 
+ <tr>
+  <td><dfn>unknown session</dfn>
+  <td>404
+  <td><code>unknown session</code>
+  <td>The requested <a>sessionId</a> did not match 
+   with any <a>sessionId</a> known by a node.
+ </tr>
+
  <tr>
   <td><dfn>unsupported operation</dfn>
   <td>500