“nofollow” relation is telling to the Google not to pass any page rank to the link you give as external link in your site. If you do not give nofollow relation in the external links means your site page rank will passes to other site and link spammers will take the advantage of your site’s page rank. Google Bot would no longer treat nofollowed links. In SEO nofollow attribute have lot of advantages. We can avoid using nofollow relation while giving in the external links to your supporting blogs, social media pages and your other authorship sites. It helps to improve the visibility of those pages in the search engine results. nofollow is one of the way of Webmasters request to the search engines for “Don’t follow this link”. Users can freely add links to any relevant site when one word or content of your site can’t express the full idea about that particular data. The main purpose of link building is you want your site links to be followed and therefore counted by Google.
Structure of nofollow relation
<a href=”http://www.example.com” rel=”nofollow”>Example</a>
When to use nofollow attribute
Paid links- Use nofollow attribute for keep links people buy on your site, even if through ads, from passing credit.
Comments- If your site allows any people to comments without measure, you can may get link drops. Using nofollow you can keeps bad sites from appearing to get credit from your site, which also avoids trouble with Google.
User generated content– Similar to comments if you allow anyone to contribute to your site without measure, nofollow can prevent your site from getting links from bad sites.
Embeds– Use nofollow if you add widgets or info graphics from other sites and don’t want to be seen as push those, if you’re not fully behind the content. “nofollow” attribute is created January 2005 by Google, yahoo, Microsoft and major blogging platforms to avoid comment spam. In 2005 September recommended by Google for use in blocking paid links. Technically it’s the attribute rather than tag.