The tag <rel=”nofollow”> is an attribute that tells a search engine crawler not to follow a certain link on your website.
For example, if you want to include an example of a bad site (like a hacker’s site or an SEO spam site) you may want to show that link on your
web site. However, that link could reduce your search engine ranking because it’s a known bad site, and when you include the link to it the crawler thinks you’re endorsing the site.
The url tag with nofollow in it is like this–
<a href=”http://www.examplebad.com”rel=”nofollow”> Bad Site </a>
The nofollow tag is’nt essential in your SEO efforts. However it could help prevent your site ranking from being reduced, and maybe even increase your ranking a little. Anything that keeps your ranking from falling is a good measure to take.