A meta tag in the HTML code of a web page that tells search engines to disregard the page. On pages such as blog posts that invite user comments, a nofollow link protects you from search engines ranking your page based on user comments you can’t control. Let’s say some users comment on your blog post to promote their own products and stuff your comments with keywords. You can use a nofollow tag to avoid search penalties.

The 3 Things To Avoid When Emailing Your List
When you decide to have an opt-in list, it is not just a matter of sending your subscribers your promotional newsletters or catalogs.