Add rel=nofollow to categories

gistfile1.aw

<?php 

/**
 * Add rel=nofollow to wp_list_categories
 * @link http://www.billerickson.net/adding-nofollow-to-category-links/
 * @author Bill Erickson
 */
function add_nofollow( $text ) {
	$text = stripslashes($text);
	$text = preg_replace_callback('|<a (.+?)>|i', 'wp_rel_nofollow_callback', $text);
	return $text;
}
add_filter( 'wp_list_categories', 'add_nofollow' );

/**
 * Add rel=nofollow to the_category
 * @link http://www.billerickson.net/adding-nofollow-to-category-links/
 * @author Bill Erickson
 */
function add_nofollow_cat( $text ) {
	$text = str_replace('rel="category tag"', "", $text);
	$text = add_nofollow($text);
	return $text;
}
add_filter( 'the_category', 'add_nofollow_cat' );