Search engines use bots called search engine spiders to rank websites according to two things.

First, search engines determine your site’s relevance to the search term. Hence, CNN’s website will rank higher than somebody’s political blog when searching for the word news.

Second, search engines take into consideration the number of websites that link back to your website. When web users type keywords into the search bar, spiders crawl through pages that contain the keywords. Then, they pull out a ranked list known as the search engine results.

Websites typically contain links. While web users can choose to click or ignore these links, search engine spiders determine whether or not to follow a link based on the presence or absence of one attribute: the nofollow tag.

The nofollow tag is not visible to the naked eye but can be seen on links if you view the source of the web page. (In fact there are now directories dedicated to listing sites that do not adhere to the nofollow rule)

Nofollow links
In principle, nofollow is an attribute that prevents search engine spiders from pulling up a website that contains a link, even if it matches the search keyword. Especially helpful for blogs, this attribute is designed to prevent spammers from benefiting from a website’s search optimization efforts. Nofollow does not affect the ranking of a website that contains nofollow links.

It should be noted that nofollow is not designed to block websites. Web users can choose to click on nofollow links and be led to the link’s site. Also, nofollow does not prevent the linked website to be indexed by search engines.

Dofollow links
Dofollow means deactivating the nofollow attribute. This allows search engine spiders to crawl over the links. When the keyword matches, the websites where dofollow links appear are included on the search engine results page. However, being crawled over does not affect the ranking of the dofollow link’s website. Those that benefit in this scenario are the websites wherein the dofollow links appear.

Although most bloggers would prefer nofollow links to protect their blogs from spammers, other bloggers have found a way to incorporate anti-spam security measures that allow them to deactivate the nofollow attribute.

Most advertisers prefer to market through dofollow blogs and websites because these sites could generate a lot of backlinking through numerous comments that can improve the advertisers’ popularity and searchability. This marketing need fuels the demand for online lists of dofollow sites and blogs.

To follow or not to follow
There is an ongoing movement that encourages webmasters and bloggers to be selective about the links that they classify as nofollow, instead of implementing a nofollow setting for all links.

Selective removal of the nofollow attribute could encourage people to write relevant comments. A lot of good comments can be a form of keywords that will bring in more traffic to your site.

Although nofollow does protect sites from excessive spamming, allowing links to be followed could start a chain of followed links that are relevant to one another thereby benefiting all sites in the long run.

Personally filtering comments could be time consuming, but it could be rewarding. You can weed out the less genuine comments and make sure that your site isn’t cluttered with too many external links. Guarding against excessive external links will protect your site’s search engine ranking.