patch.diff

--- link-template.php	2009-01-24 01:33:37.000000000 -0800
+++ link-template.php	2009-05-30 11:10:41.000000000 -0700
@@ -950,6 +950,9 @@
 	else
 		$post = get_adjacent_post($in_same_cat, $excluded_categories, $previous);
 
+	$rel = 'next';
+	if($previous) $rel = 'prev';
+
 	if ( !$post )
 		return;
 
@@ -961,7 +964,7 @@
 	$title = apply_filters('the_title', $title, $post);
 	$date = mysql2date(get_option('date_format'), $post->post_date);
 
-	$string = '<a href="'.get_permalink($post).'">';
+	$string = '<a rel="'.$rel.'" href="'.get_permalink($post).'">';
 	$link = str_replace('%title', $title, $link);
 	$link = str_replace('%date', $date, $link);
 	$link = $string . $link . '</a>';

plugin.php

<?php
/*
Plugin Name: rel=prev/next
Plugin URI: http://singpolyma.net/plugins/
Description: Adds rel/prev/next to next/previous posts links
Version: 0.1
Author: Stephen Paul Weber
Author URI: http://singpolyma.net
License: MIT license (http://www.opensource.org/licenses/mit-license.php)
*/

add_filter('next_posts_link_attributes', 'get_next_posts_link_attributes');
add_filter('previous_posts_link_attributes', 'get_previous_posts_link_attributes');

if (!function_exists('get_next_posts_link_attributes')){
	function get_next_posts_link_attributes($attr){
		$attr .= 'rel="prev"';
		return $attr;
	}
}
if (!function_exists('get_previous_posts_link_attributes')){
	function get_previous_posts_link_attributes($attr){
		$attr .= 'rel="next"';
		return $attr;
	}
}

?>

Thats work, nice but need to little change 'rel="prev"'; to 'rel="next"';

if (!function_exists('get_next_posts_link_attributes')){
	function get_next_posts_link_attributes($attr){
		$attr .= 'rel="prev"';
		return $attr;
	}
}
if (!function_exists('get_previous_posts_link_attributes')){
	function get_previous_posts_link_attributes($attr){
		$attr .= 'rel="next"';
		return $attr;
	}
}

to

if (!function_exists('get_next_posts_link_attributes')){
	function get_next_posts_link_attributes($attr){
		$attr .= 'rel="next"';
		return $attr;
	}
}
if (!function_exists('get_previous_posts_link_attributes')){
	function get_previous_posts_link_attributes($attr){
		$attr .= 'rel="prev"';
		return $attr;
	}
}

use it on www.whatisthewik.com and work, thanks singpolyma