Index: modules/system/system-behavior.css
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system-behavior.css,v
retrieving revision 1.13
diff -u -r1.13 system-behavior.css
--- modules/system/system-behavior.css	9 Aug 2010 16:58:15 -0000	1.13
+++ modules/system/system-behavior.css	15 Sep 2010 17:39:53 -0000
@@ -313,3 +313,13 @@
   clip: rect(1px 1px 1px 1px); /* IE6, IE7 */
   clip: rect(1px, 1px, 1px, 1px);
 }
+
+/**
+ * The .focusable class extends the .element-invisble class to allow the element
+ * to be focusable when navigated to via the keyboard.
+ */
+.element-invisible.focusable:active,
+.element-invisible.focusable:focus {
+  position: static !important;
+  clip: auto;
+}