Index: modules/block/block.admin.inc
===================================================================
RCS file: /cvs/drupal/drupal/modules/block/block.admin.inc,v
retrieving revision 1.72
diff -u -p -r1.72 block.admin.inc
--- modules/block/block.admin.inc	15 Jan 2010 10:59:21 -0000	1.72
+++ modules/block/block.admin.inc	9 Feb 2010 12:54:12 -0000
@@ -11,7 +11,7 @@
  */
 function block_admin_demo($theme = NULL) {
   drupal_add_css(drupal_get_path('module', 'block') . '/block.css', array('preprocess' => FALSE));
-  return '';
+  return l(t('Return to the block administration page'), 'admin/structure/block/list/' . $theme, array('attributes' => array('class' => 'block-back-to-list')));
 }
 
 /**