Index: modules/system/system.css
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.css,v
retrieving revision 1.56
diff -u -p -r1.56 system.css
--- modules/system/system.css	31 Jul 2009 11:20:42 -0000	1.56
+++ modules/system/system.css	2 Aug 2009 21:17:25 -0000
@@ -564,3 +564,24 @@ div.password-suggestions ul {
 div.password-confirm {
   visibility: hidden;
 }
+
+/**
+ * Hide elements from all users.
+ *
+ * To be used for elements that should not be displayed to any user.
+ */
+.element-hidden {
+  display: none;
+}
+
+/**
+ * Hide elements visually, but keep them available for screen-readers.
+ *
+ * Used for information required for screen-reader users to understand and use
+ * the site where visual display is undesirable. Information provided in this
+ * manner should be kept concise, to avoid unnecessary burden on the user.
+ */
+.element-invisible {
+  height: 0;
+  overflow: hidden;
+}