Rel nofollow - What does this mean?

Preventing Comment and Link Spam on Sites

A few years ago, search engines started using links and link popularity to affect placement in their indexes. And of course, as soon as spammers figured this out, they started trying to find ways to get around it or improve their rankings artificially. One way to do this is to add the links themselves—in the comments.

The major search engine providers (Google, Yahoo!, and MSN) got together and came up with a way to fight this form of link spam - the rel="nofollow" attribute.

And now, most blog software programs add this attribute to links in comments automatically.

What Does the rel="nofollow" Attribute Do?

When a search engine spider comes to a page with links on it, the standard response is to index the page and then follow all the links on the page. That is when the search engine looks at the links to see which ones you have “voted” for by putting them on your page. When the search engine spider sees nofollow on the link, it does the following:

  1. Does not follow the link to the new site
  2. Does not count the link towards it’s popularity score in their ranking engine
  3. Does not include the link text in the relevancy score for those keywords

Search engines will not penalize your site or blog for links that have nofollow on them. It also doesn’t prevent a site from ever being indexed in Google. And putting nofollow on links does not imply any judgement about those links.

In other words, if you apply the nofollow attribute to a link you aren’t saying that you think it’s bad or spam, just that the link isn’t yours and shouldn’t be followed by search engines.

Why Do You Want nofollow Links on Comments

The most important reason to add nofollow to your comment links is to discourage spammers.

No, this won’t stop them altogether (I don’t think anything stops them), but it will discourage them a little bit. As while they can get their link on your page (assuming it isn’t filtered by a spam filter also on your site), the link itself won’t help them beyond the possibility that someone might click on it.

You don’t have to rely only on your blog software to flag comment links. You can use the attribute anywhere on your site you want to. The best places to use it are on external links that you want to include on your site but don’t want to send to search engines, places like forums, chat, and other user generated content most often.

Where Should You Put nofollow

Most search engines recommend that you put the rel="nofollow" attribute on any links that come from a source you don’t vouch for, such as:

  • comments
  • forums
  • other user generated content

You should also put rel="nofollow" on links that point to advertising, as a search engine robot following the link could be a violation of your advertising agreement.

Finally, it's a good idea to put rel="nofollow" on links to things that a search engine spider can't do, such as registration forms or forum login pages.