Index: sites/default/default.settings.php
===================================================================
RCS file: /cvs/drupal/drupal/sites/default/default.settings.php,v
retrieving revision 1.51
diff -u -p -r1.51 default.settings.php
--- sites/default/default.settings.php	11 Oct 2010 23:49:48 -0000	1.51
+++ sites/default/default.settings.php	22 Dec 2010 21:14:57 -0000
@@ -286,9 +286,10 @@ ini_set('session.cookie_lifetime', 20000
  * the same Drupal site, you can either redirect them all to a single domain
  * (see comment in .htaccess), or uncomment the line below and specify their
  * shared base domain. Doing so assures that users remain logged in as they
- * cross between your various domains.
+ * cross between your various domains. Make sure to always start
+ * $cookie_domain with a leading dot.
  */
-# $cookie_domain = 'example.com';
+# $cookie_domain = '.example.com';
 
 /**
  * Variable overrides: