rel=”nofollow” tag a message for search engines

The nofollow tag is an HTML attribute value used to instruct some search engines that do not follow this link and do not give it any credit in terms of ranking influence.
its usage is very simple like Link

This tag was introduced by Google to fight the spames and now is being respected by other search engines as well. This tag rel=”nofollow” help search engine that to distinguish between links which are trusted andthe other whic are not to assigne rank and other seo influence . Google does not count these links as backlinks which are assigned by this method.

This tag is important for forums, blogs and link selling as you may or may not wish to give a backlink credit to an untrusted or unknown site.