Blogroll in WordPress displays a list of blogger’s favorite blogs in the sidebar of their blog. Blogroll provides links to external blogs in easily managed way. Some webmasters also use Blogroll to display backlinks to other external sites for link exchange or link buying. In reality, links added by WordPress blogroll is actually useless textlinks that are discouraged by Google and most other search engines, especially when the links are paid off or in exchange for a link back.

Thus, linking blindly to external sites MAY (if your blog or website has been caught and labeled by Google machine algorithm as participate in illegal link scheme to boost page rank, although you’re not) severely and negatively discount your own site PageRank (PR) value, or worst, affects your site ranking in search engine results positioning. To avoid any potential backlash from the external links in Blogroll, it’s best to add rel=”nofollow” attribute to the <a> tag in Blogroll as suggested by Google so that no PageRank value is passed through the links, and the links won’t penalize your site ranking.

To automatically add and attach rel=”nofollow” attribute to each and every outgoing links in Blogroll, we need to hack through WordPress core source code file. Go to wp-includes/ directory of your blog root folder, then edit the bookmark-template.php file with any text editor such as vi.

Locate the following line (it’s at line 48 for WordPress version 2.3.1):

$output .= '<a href="' . $the_link . '"' . $rel . $title . $target. '>';

Append the rel=”nofollow” to the line by changing the line to the following:

$output .= '<a href="' . $the_link . '"' . $rel . $title . $target. ' rel="nofollow">';

Save the file when done.

All Blogroll links in blog sidebar will now have rel=”nofollow” attribute tagged with the link, which force search engine spiders and crawlers to stop following the links. Adding the nofollow attribute may not change the fortune of your site immediately, but will surely reduce the risks of been penalized by search engines for excessive linking.

Update: It’s not recommended to modify the core files of WordPress. Thus, it’s recommended to use a plugin which adds nofollow attribute automatically, which there are plenty.