The nofollow tag is a way that publishers can inform Google and other search engines that they do not endorse certain links to other pages.
Nofollow is important for search engine optimisation as it proves to search engines that they are not selling influence or are involved in schemes deemed as unacceptable SEO practices.
By attaching a nofollow tag, you are essentially telling search engines to ignore this link. This means that nofollow links have do not affect your sites page rankings.
Nofollow tags were introduced to HTML in 2005 by Google, Yahoo, Microsoft and major blogging sites primarily to prevent comment spam in blogs. They aimed to make the lives of spammers more difficult, so that when they spammed blogs and forums with unwanted links in the comments section (a standard spam tactic), it would not affect the ranking of a site. Prior to nofollow, preventing robots from following individual links on a page required a great deal of effort.
Matt Cutts, former head of the web spam team at Google, said at the time: “The nofollow tag allows a site to add a link that abstains from being an editorial vote. Using nofollow is a safe way to buy links, because it’s a machine-readable way to specify that a link doesn’t have to be counted as a vote by a search engine.”
When you should use nofollow instructions
According to Google’s Webmaster Guidelines, nofollow tags should be used on content you cannot vouch for, such as user-generated content, i.e. blog comment sections and external ad links. In essence, websites should apply nofollow tags to links they don’t want Google to consider a vote of trust.
The value of nofollow tags to Google ranking is debatable. Google maintain they do not count nofollow links and any authority associated with a nofollowed link is discarded. However, many in SEO believe that in some cases there is some value being placed on nofollowed links.
Our advice is to always ensure there are nofollow instructions on advertising banners or outright promotions. Your account manager will be able to advise you on the use of these tags on a case-by-case basis.
How you should use nofollow instructions
Nofollow tags are assigned to the rel (short for relevance) attribute of an HTML element. Rel attributes are used by search engines to get more information about a link, it is a way of defining the relationship between your website and the page being linked to.
Here’s how a nofollow link differs from default links in HTML:
Default link: <a href=”link”>text</a>
No followed link: <a href=”link” rel=”nofollow”>text</a>