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Hi Joanne Nofollow attribute is very important ,  "Nofollow" is generally used to tell search engines Don't follow links on this page. You don't trust on links which are linking to your site. So you can discourage untrusted user comments or guestbook entries in your comment page . If you want to use "Follow" then you have to moderate each and every comment on your page so Nofollow is batter option.