Index: wp-includes/author-template.php
===================================================================
--- wp-includes/author-template.php	(revision 20450)
+++ wp-includes/author-template.php	(working copy)
@@ -140,7 +140,7 @@
  */
 function get_the_author_link() {
 	if ( get_the_author_meta('url') ) {
-		return '<a href="' . get_the_author_meta('url') . '" title="' . esc_attr( sprintf(__("Visit %s&#8217;s website"), get_the_author()) ) . '" rel="external">' . get_the_author() . '</a>';
+		return '<a href="' . get_the_author_meta('url') . '" title="' . esc_attr( sprintf(__("Visit %s&#8217;s website"), get_the_author()) ) . '" rel="author external">' . get_the_author() . '</a>';
 	} else {
 		return get_the_author();
 	}