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Nofollow Reciprocity

WordPress Blog SEO Plugin Adding 'nofollow' tags to External Links To Wikipedia, StumbleUpon, Delicious...

These sites, in addition to not giving you any credit, also DEVASTATE your site PageRank and SERP position.

Most big sites by default use 'nofollow' tags therefore not trusting external links nor users that post those links there. This means that they don't give any credit (in the form of PageRank) to those links and are essentially considering them spam (as that was 'officially' the purpose of 'nofollow' tag introduction - actually messing with the blogging community search engine rankings was the real purpose). This results in their pages appearing higher in search engine results and your pages appearing lower.

This plugin detects links to above mentioned sites, and puts 'nofollow' tags on them. 'Do unto others as you would have others do unto you.' WordPress is a major blogging platform, with tens of millions of users. If many people using WordPress use this plugin, other big sites may reconsider their 'nofollow' strategy. This plugin expands on Wikipedia nofollow plugin hacked by a revolted blogger.

Current sites on the list are:

addthis.com,
blinklist.com, blogger.com,
del.icio.us,
facebook.com,
google.com,
linkter.hu,
ma.gnolia.com,
netvouz.com,
segnalo.alice.it, simply.com, shadows.com, startaid.com, stumbleupon.com,
~~thisnext.com~~,
wikipedia.org,
yahoo.com, youtube.com

If I am missing some major web-sites, please let me know by sending a message at the form below. Note that this list includes sites that have 'nofollow' tags in external links provided by users, whether they are links to news, stories, user homepages, etc. You can easily add your own 'black list' sites in the code of the downloaded file.

Copy (CTRL+C) code below and save it into file named 'nofollow-reciprocity.php'

<?php

/*
Plugin Name: Nofollow reciprocity
Plugin URI: http://www.inverudio.com/programs/WordPressBlog/NofollowReciprocity.php
Description: Searches for links to large sites using 'nofollow' tags for external links, and puts the same tag on links to those sites (Wikipedia.org, StumbleUpon.com, and similar)
Author: Lazar Kovacevic(based on 2 plugins quoted below)
Version: 1.0
Author URI: http://www.inverudio.com
*/

/* Based on:

Plugin Name: Wikipedia nofollow
Plugin URI: http://whatjapanthinks.com/wikipedia-nofollow/
Description: Searches for links to Wikipedia.org, and adds a rel="nofollow" tag if necessary
Author: Ken Yasumoto-Nicolson (based on Identify External Links by Mark Jaquith)
Version: 1.0
Author URI: http://whatjapanthinks.com


Plugin Name: Identify External Links
Plugin URI: http://txfx.net/code/wordpress/identify-external-links/
Description: Searches the text for links outside of the domain of the blog.	 To these, it adds <strong>class="extlink"</strong> (and optionally, <strong>target="_blank"</strong>).
Author: Mark Jaquith
Version: 1.3
Author URI: http://txfx.net/
*/

/*	Copyright 2005	Mark Jaquith (email: mark.gpl@txfx.net)
   Additional changes Copyright 2007 Ken Yasumoto-Nicolson (email: seron@whatjapanthinks.com)

	This program is free software; you can redistribute it and/or modify
	it under the terms of the GNU General Public License as published by
	the Free Software Foundation; either version 2 of the License, or
	(at your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
	GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with this program; if not, write to the Free Software
	Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

function wp_get_domain_name_from_uri($uri){
	preg_match("/^(http:\/\/)?([^\/]+)/i", $uri, $matches);
	$host = $matches[2];
	preg_match("/[^\.\/]+\.[^\.\/]+$/", $host, $matches);
	return $matches[0];	   
}

function wp_has_no_rel_nofollow($text)
{
	if ( preg_match("/rel=[\"\'].*?nofollow.*?[\"\']/i", $text ) )
		return false;
	else
		return true;
}

function wp_inarray($needle, $array, $searchKey = false)
{
   if ($searchKey) {
       foreach ($array as $key => $value)
           if (stristr($key, $needle)) {return $key;}
       }
   else {
       foreach ($array as $value)
           if (stristr($value, $needle)) {return $value;}
       }
   return '';
}

function parse_nofollow_reciprocity($matches)
{

	//add in next line's array sites that you think do not deserve credit because they don't give it to other sites.
	if ( 	wp_inarray(wp_get_domain_name_from_uri($matches[3]), array("wikipedia.org","del.icio.us","stumbleupon.com","ma.gnolia.com","simply.com","blinklist.com","startaid.com","netvouz.com","facebook.com","shadows.com","yahoo.com","google.com","thisnext.com-removed-due-to-users-feedback","linkter.hu","segnalo.alice.it","addthis.com","youtube.com","blogger.com")) &&
		  wp_has_no_rel_nofollow( $matches[1] ) &&
		  wp_has_no_rel_nofollow( $matches[4] ) )
	{
		return '<a rel="nofollow" href="' . $matches[2] . '//' . $matches[3] . '" ' . $matches[1] . $matches[4] . '>' . $matches[5] . '</a>';
	}
	else
	{
		// Do nothing
		return '<a href="' . $matches[2] . '//' . $matches[3] . '" ' . $matches[1] . $matches[4] . '>' . $matches[5] . '</a>';
	}
}
	

function wp_nofollow_reciprocity($text) 
{
	$pattern = '/<a (.*?)href=[\"\'](.*?)\/\/(.*?)[\"\'](.*?)>(.*?)<\/a>/i';
	$text = preg_replace_callback($pattern,'parse_nofollow_reciprocity',$text);
	return $text;
}

// filters have high priority to make sure that any markup plugins like Textile or Markdown have already created the HTML links
add_filter('the_content', 'wp_nofollow_reciprocity', 999);
add_filter('the_excerpt', 'wp_nofollow_reciprocity', 999);

// delete this one if you don't want it run on comments
add_filter('comment_text', 'wp_nofollow_reciprocity', 999);

?>

Copy that file into WordPress plugins folder, activate plugin, and watch blog statistics.

Remember to delete WP-Cache if you have that plugin. Otherwise, you may not see effect of this plugin immediately.

If you want to add this tags in comment author's url's whose link point to above sites, add at the end of above code: add_filter('get_comment_author_link', 'wp_nofollow_reciprocity', 999);

Comments from past visitors:

Q: The inclusion of ThisNext isn't entirely fair. While stores are "no-followed" to reduce the incentive for gaming the system, user's personal blogs and "via" attributions are left alone. You can see both on this page: http://www.thisnext.com/by/whosdiary/
A: Thanks for the note! I am not familiar with all web-sites on the list above, but have just looked quickly thru the major social web-sites. I will remove 'ThisNext' from the list. As I am kind of 'lazy' to zip the file after each modification, and upload it here, instead of downloading zip file, visitors should copy/paste the code from the box above which has most recent list.

Leave comments and suggestions below. If you write your email in the message, I'll let you know about modified file.

For another SEO plugin, see New Tab/Window Target Blank Plugin.

Nofollow Reciprocity

WordPress Blog SEO Plugin Adding 'nofollow' tags to External Links To Wikipedia, StumbleUpon, Delicious...

Comments from past visitors:

Comments, questions, suggestions ?