Index: modules/forum/forum-list.tpl.php
===================================================================
RCS file: /cvs/drupal/drupal/modules/forum/forum-list.tpl.php,v
retrieving revision 1.5
diff -u -p -r1.5 forum-list.tpl.php
--- modules/forum/forum-list.tpl.php	13 Oct 2008 12:31:42 -0000	1.5
+++ modules/forum/forum-list.tpl.php	6 Jul 2010 17:00:51 -0000
@@ -34,10 +34,10 @@
 <table id="forum-<?php print $forum_id; ?>">
   <thead>
     <tr>
-      <th><?php print t('Forum'); ?></th>
-      <th><?php print t('Topics');?></th>
-      <th><?php print t('Posts'); ?></th>
-      <th><?php print t('Last post'); ?></th>
+      <th scope="col"><?php print t('Forum'); ?></th>
+      <th scope="col"><?php print t('Topics');?></th>
+      <th scope="col"><?php print t('Posts'); ?></th>
+      <th scope="col"><?php print t('Last post'); ?></th>
     </tr>
   </thead>
   <tbody>
Index: modules/forum/forum.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/forum/forum.module,v
retrieving revision 1.567
diff -u -p -r1.567 forum.module
--- modules/forum/forum.module	20 Jun 2010 23:55:08 -0000	1.567
+++ modules/forum/forum.module	6 Jul 2010 17:00:51 -0000
@@ -867,10 +867,10 @@ function forum_get_topics($tid, $sortby,
   global $user, $forum_topic_list_header;
 
   $forum_topic_list_header = array(
-    NULL,
-    array('data' => t('Topic'), 'field' => 'f.title'),
-    array('data' => t('Replies'), 'field' => 'f.comment_count'),
-    array('data' => t('Last reply'), 'field' => 'f.last_comment_timestamp'),
+    array('data' => t('Type'), 'field' => null, 'class' => 'element-invisible', 'scope' => 'col'),
+    array('data' => t('Topic'), 'field' => 'f.title', 'scope' => 'col'),
+    array('data' => t('Replies'), 'field' => 'f.comment_count', 'scope' => 'col'),
+    array('data' => t('Last reply'), 'field' => 'f.last_comment_timestamp', 'scope' => 'col'),
   );
 
   $order = _forum_get_topic_order($sortby);