Not many people would deny the impact of internet marketing techniques. It not only created new ways for businesses from all around the world to have access to millions of potential customers. It also opened a floodgate that has been difficult to close; online spam.
As certain fora started having increased authority among users, links posted on comment sections were seen as upvotes given to trusted sites. It is only natural for people to share interesting links they find on the internet. If the forum was particularly popular, these links could get some of its ranking power transferred, creating a win-win situation. But not for long.
The Spam problem
Some people say that if they included links in irrelevant posts to lure potential visitors to every forum, it would allow them to siphon some of their ranking power in search engines. This soon led to a spamming nightmare. Spammers tried to flood every popular topic with solicitation in some form, rendering them virtually useless to legitimate readers.
Webmasters had a hard time redirecting these links to URLs that were blocked in their robots.txt. Just imagine constantly having to delete or redirect these spam links 24/7. The rel=” no follow” attribute was an attempt to solve this by giving webmasters more control by instructing bots not to crawl certain links.
With time, search engines and web developers started fighting irrelevant and repetitive content created by spammers to keep them away from sites people visit for informative or recreative ends. Just like many elemental microformats, rel-nofollow was created to be inserted into website codes to solve a single issue: spamdexing. More specifically link spamming.
It worked really well for forums, guest books and the like. But spammers did not stop there. Later, they applied their black hat practices in places like Wikipedia and Yahoo Answers. Spammers ultimately forced many sites to add the “No Follow” attribute to comments and user-generated content.
Many users took it negatively as legit contributors saw their own links being depreciated. However, it greatly discouraged spammers from targeting sites that used the attribute. Nowadays it is hard to find a site set to allow follow links, and Google does not trust that much liberty given to contributors as they have a good memory.
How Search Engines treat “No Follow”
All major search engines acknowledged and supported the “No Follow” from the beginning. However, each one treats it in a slightly different way.
The tech giant has stated that its crawlers take these NoFollow links literally. This attribute makes it possible to prevent links from getting upvotes for PageRank purposes. Imagine that Google has an all-encompassing graph that indicates page ranking on the whole web. The NoFollow attribute targets untrusted links so they are not reflected on this graph.
It does not mean that target links do not get to the index. If any other sites link to them, crawlers will certainly index and map them.
Yahoo uses a different line of thought. Their bots do follow the target links and crawl the page to discover content that might be useful for other users. However, it does not consider it as an upvote for ranking purposes. They implemented this as a spam defense in their Yahoo Answers site, for example. They apply the “No Follow” attribute to comments made by most of their contributors. However, they have learned to apply certain limitations to people who have earned enough reputation and trust in their community.
Microsoft´s bet on the search engine market works pretty much the same as Google. Bing doesn’t crawl the target link and excludes it for ranking purposes. However, Bing indexes the site if others link to it. That makes it possible for users to find them if they.
Working with NoFollow
If you wonder where to put this attribute to good use, Google made some great and creative suggestions. To avoid comment spam, they recommend using “No Follow” on content webmasters do not want to vouch for. Normally this is content found on guestbook entries, comment sections, and such.
Paid links are also a no-no as they should never count as an editorial confidence vote. Google penalizes sites that buy links for building traffic or support other sites. So, this attribute tells engines that you are not using your paid links to manipulate rankings.
As has happened to virtually everything in the online world, rel=nofollow has also been used for things other than its original intent.
Soon, many applied it to paid links. Then to pages that should be only shown after visitors fill up a form or perform an action. “Thank You” pages are a good example of these. It would not make much sense to show them to users who have not interacted with the website before.
But here is where it gets weird. Some people have advanced the theory that it is possible to use this attribute for effectively managing link juice within a website. By applying NoFollow to some inbound links, one could theoretically redirect PageRank value to the links that really mattered within our site´s structure. People in the SEO universe called this PageRank Sculpting. They recommended it as a real panacea for every marketer back in the day.
However, it has been noticed that it does not do much to benefit a website, and even Google says it is a bad idea to work around that theory.