To block search engines from following a link on your website, add a rel=”nofollow” tag to your HTML code.
This is useful if you want to have links on your page to external sources. Use the following syntax for example:
<a href="http://www.externalsite.com" rel="nofollow">External site</a>
By doing this, your visitors will be able to use the link, but the search engines will not “follow” it.
You can use this approach to add links to your website to competitive sites without increasing their page rank.