Index: includes/form.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/form.inc,v
retrieving revision 1.367
diff -u -p -r1.367 form.inc
--- includes/form.inc	27 Aug 2009 04:40:12 -0000	1.367
+++ includes/form.inc	28 Aug 2009 14:48:10 -0000
@@ -2333,7 +2333,9 @@ function theme_vertical_tabs($element) {
   // Add required JavaScript and Stylesheet.
   drupal_add_library('system', 'vertical-tabs');
 
-  return '<div class="vertical-tabs-panes">' . $element['#children'] . '</div>';
+  $output = '<h2 class="element-invisible">' . t('Tab strip') . '</h2>';
+  $output .= '<div class="vertical-tabs-panes">' . $element['#children'] . '</div>';
+  return $output;
 }
 
 /**