Index: wp-admin/edit-link-form.php
===================================================================
--- wp-admin/edit-link-form.php	(revision 20831)
+++ wp-admin/edit-link-form.php	(working copy)
@@ -62,7 +62,9 @@
 <h2><?php echo esc_html( $title ); ?>  <a href="link-add.php" class="add-new-h2"><?php echo esc_html_x('Add New', 'link'); ?></a></h2>
 
 <?php if ( isset( $_GET['added'] ) ) : ?>
-<div id="message" class="updated"><p><?php _e('Link added.'); ?></p></div>
+<div id="message" class="updated"><p><?php _e( 'Link added.' ); ?></p></div>
+<?php elseif ( isset( $_GET['error'] ) ) : ?>
+<div id="message" class="error"><p><?php _e( 'Could not add link. Make sure you specify a link name and address.' ); ?></p></div>
 <?php endif; ?>
 
 <?php
Index: wp-admin/link.php
===================================================================
--- wp-admin/link.php	(revision 20831)
+++ wp-admin/link.php	(working copy)
@@ -70,6 +70,8 @@
 		$redir = wp_get_referer();
 		if ( add_link() )
 			$redir = add_query_arg( 'added', 'true', $redir );
+		else
+			$redir = add_query_arg( 'error', 'true', $redir );
 
 		wp_redirect( $redir );
 		exit;