The code to use nofollow on a link appears like
Nofollow can also be used in a robots meta tag to prevent a search engine from counting any outbound links on a page. This code would look like this
Google’s Matt Cutts also pushes webmasters to use nofollow on any paid links, but since Google is the world’s largest link broker, their advice on how other people should buy or sell links should be taken with a grain of salt. Please note that it is generally not advised to practice link hoarding as that may look quite unnatural. Outbound links may also boost your relevancy scores in some search engines.