Index.rst: fixed broken reference

extension/Documentation/UsersManual/Index.rst

@@ -982,7 +982,7 @@ Type: text
   * *retype=1* (optional): Current input element will be rendered twice. The form can only submitted if both elements are equal.
   * *retypeLabel=<text>* (optional): The label of the second element.
   * *retypeNote=<text>* (optional): The note of the second element.
-  * Also check the  :ref:`_fe-parameter-attributes` *data-...-error* to customize error messages shown by the validator.
+  * Also check the  :ref:`fe-parameter-attributes` *data-...-error* to customize error messages shown by the validator.
 
 Type: editor
 ^^^^^^^^^^^^