Index: modules/system/system.css
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.css,v
retrieving revision 1.55
diff -u -p -r1.55 system.css
--- modules/system/system.css	20 Jul 2009 18:51:34 -0000	1.55
+++ modules/system/system.css	29 Jul 2009 07:09:28 -0000
@@ -564,3 +564,13 @@ div.password-suggestions ul {
 div.password-confirm {
   visibility: hidden;
 }
+/**
+ * Classes to hide elements and to make elements invisible. Invisible elements are still available to screen-reader users.
+ */
+.hidden {
+  display: none;
+}
+.visibility-invisible {
+  height: 0;
+  overflow: hidden;
+}