The rel=nofollow tag is simple way for webmasters to tell search engines which links or pages of links should be ignored. The configuration of both outbound and internal links on your website is important from an SEO standpoint and the no-follow tag plays a large role in that.
The no-follow tag can be implemented at the page level through a meta tag in the head section of the page. This instructs search engine spiders to not follow any links found on the page regardless of where they lead. The syntax is as follows (no pun intended) <meta name=”robots” content=”nofollow” />.
When first introduced the no follow tag was not really used on a link by link basis. As search engine optimization came further to the front of webmaster’s minds, they started using it on links when it wasn’t necessary for search engine spiders to ignore links on a page-wide basis.
So there isn’t technically a “do-follow” tag. All links that have not been deemed no-follow are then seen as do-follow by search engines. If you want links from page to page in your site (or leading to other sites) to be do-follow, you don’t have to do anything. Just leave them the way they are.
When it relates to SEO, the important thing to remember is that do-follow links pass PageRank to the pages they are connected to. That means that in the eyes of a search engine, a do-follow link counts as a vote for the page that it is linked to (regardless of whether that page is on the same domain as the linking page).
Google has a running list on their support site of scenarios where rel=”nofollow” should be used. You can read in detail why they make the suggestions that they do but here is the short list.
Use no-follow when:
• Linking to untrusted content
• When you have links that are paid (such as ads)
• Links that don’t make sense for search spiders to follow such as registration links or support form links.
There are some other times you should use the no-follow tag besides what Google suggests. These include scenarios both on and off your domain.
If you have a link leading to a keyword competitor’s site, it’s probably a good idea to not flow PageRank to that page (especially if you are using exact match anchor text). You want to rank well for your target keywords and not necessarily help others do it.
If you have a commenting plugin on a WordPress blog your comments should be no-follow by default. Just be sure that’s true and if you have some other commenting mechanism, make sure it creates no-follow links automatically for users.
Comment spam is a huge problem for reputable site and blog owners. Of course you should make links do-follow for those that deserve it but set thing up so you can do that manually.
If you have a review plugin on your site, you should make that configure links as no-follow by default. Again, you can change things later if you want. Remember that any time there is a link leading from your domain to another configured as do-follow it appears to search engines that you are endorsing that other website. You want to be sure you are making good endorsements.
This falls under Google’s definition of “untrusted content”. Make it a practice to inspect any links leading out from your site to other domains. Check those sites out and make sure 1) that you want to be linking to them at all and 2) that they are reputable and using good SEO practices.
A while back, Matt Cutts wrote an interesting post on his personal blog about PageRank sculpting. The post is very dated but a lot of the concepts remain the same and there are also some good comments on the post. Essentially you want to link your pages in a way (leveraging no-follow) that helps PageRank flow throughout your site.
There are some pages on any site that really don’t need to be worked on from an SEO standpoint. Pages like privacy policies, contact us, logins, registrations and other similar pages should have their links no-followed in main and footer navigation as well as any other places they are linked to on the site.
This isn’t a hard rule and you may find varying opinions about it on the web. The main thing to remember is that you shouldn’t flow PR to pages that have no real benefit to users in terms of content that they might be searching for online. If your contact page has tons of useful content on it (i.e. addresses, phone numbers and the like), then by all means make links leading there do-follow.
While there may not be a definitive source on this, having a ton of do-follow links all pointing at the same pages on your site is unbalanced. For example you might have site-wide links that all point at a an about us page along with an FAQ page that points at the same page. Really only the highest PR page that is relevant need be pointing at another page with a do-follow link. The others can be no-followed.
The no-follow tag can be a valuable tool for crafting PageRank flow through your website. I can also help you link to sources elsewhere on the web safely.