Link buying and exchanging is a good idea but may be not for the search engines. Got it? well lets take a simple example of blogroll in WordPress. Blogroll is a list of links that may be links of other bloggers, favorite website, link buying or exchanging. Be careful if your website caught by the search engine algorithm as illegal link exchanging scheme (although you may not doing this). So this may cause of dropping your own website page rank (PR). To save you page rank (PR) use “nofollow” to all external website links, here is an example how to use “nofollow”
Link with nofollow attribute: <a href=”#” rel=”nofollow”></a>
How we can add “nofollow” automatically to the Blogroll list of links, we need to modify some code manually in the WordPress source code file. Go to the wp-includes directory of your worpress find the file with the name bookmark-template.php and open it in your favorite editor.
Worpress 2.3.1 Go to the line no. 48
Wordpress 2.6 Goto the line no. 93
Wordpress 2.7.1 Goto the line no. 99
and find some code like this
$output .= ‘<a href=”‘ . $the_link . ‘”‘ . $rel . $title . $target. ‘>’;
and change it to
$output .= ‘<a href=”‘ . $the_link . ‘”‘ . $rel . $title . $target. ‘ rel=”nofollow”>’;
save the file and you are done, from now on all your Blogroll links will have rel=”nofollow” attribute and this will reduce the risks of dropping page rank penalized by search engines.