Links can be provided in HTML code together with a nofollow attribute. This attribute ensures that search engines cannot follow the link and therefore:
the link will not be classed as a backlink for the linked website
if nofollow backlinks are used exclusively, the linked website will not be included in the index
Nofollow backlinks will not improve a website’s position in the search rankings. Nevertheless, they are necessary. They ensure that search engines perceive a site’s link building structure to be ‘natural’. In addition, nofollow backlinks contribute to visitors of other websites being forwarded to your site.
For example: in forums and blogs, the history of a lot of entries and comments is published for the sole purpose of gaining new backlinks for the website. This is why forums and blogs frequently use the nofollow attribute.
