Index: vertical-tabs.js
===================================================================
RCS file: /cvs/drupal/drupal/misc/vertical-tabs.js,v
retrieving revision 1.7
diff -u -r1.7 vertical-tabs.js
--- vertical-tabs.js	31 Aug 2009 05:51:08 -0000	1.7
+++ vertical-tabs.js	10 Sep 2009 15:26:45 -0000
@@ -108,7 +108,7 @@
  */
 Drupal.theme.prototype.verticalTab = function (settings) {
   var tab = {};
-  tab.item = $('<li class="vertical-tab-button"></li>')
+  tab.item = $('<li class="vertical-tab-button" tabindex="-1"></li>')
     .append(tab.link = $('<a href="#"></a>')
       .append(tab.title = $('<strong></strong>').text(settings.title))
       .append(tab.summary = $('<small class="summary"></small>')