Nofollow is an element that you can add to your links, this is basically stopping your link acting as a vote,
adding a nofollow is saying to the search engine, here is a link, but don't pass on credit.
Webmasters have made comment areas and whole websites such as digg, nofollow. This is to reduce the amount of
spammers. Spammers are always looking for forums, websites and blogs that are not nofollow. Digg removes the
nofollow from links that have gained trust.
I never use nofollow unless I am linking to a bad website or I have a comment area that is getting out of
Always use nofollow on advertisements so you can't be accused of supplying paid links.