SEO link building is a strategy you can use to improve your website ranking in the search engines. A link pointing back to your website is considered to be a positive “vote” for the content on your page. Search engines like Google, advanced as they are, still cannot really tell the difference between well-written useful content and trash, so they use link popularity as one factor to determine whether content is good quality or not. By getting as many positive votes or links back to your site as possible, you increase the rank of your web page in the search engine and thus increase the free traffic you will receive.
It is also important to understand that not all links are equal. There are two factors that have an impact on the importance of a link, although in the end we must guess at just how much these things really affect your ranking because Google and the other search engines never fully reveal how their ranking system is weighted to prevent link building schemes and techniques to manipulate the search index. They offer-up little hints and give you basic direction in their guidelines, but ultimately you must distill all this information for yourself to arrive at your own conclusion.
Which Factors really matter for link building?
Other SEO experts have produced complicated link building plans that capitalize on long lists of possible factors that influence the value of a link, but I prefer to just keep things simple, so I will share what works for me. My belief is that the three most important factors that affect links are the page-rank of the page providing the link, the actual content on the page surrounding the link, and the existence of the no-follow tag attached to the link.
Generally, the higher the page rank of a page, the more valuable any links on that page will be. Of course, like any rule, there are exceptions. If a high page-rank page contains 10 outbound links, those links are likely to be quite powerful. If that same page contains 500 outbound links, the links are diluted to the point where they are basically worthless, so you must take this into account in your link building plan.
Think of it like this, a page has X number of points based upon its page rank. For our example, let’s say that the page has 100 points. If there are 10 external links on that page, it is sharing its points with those 1- links, so each link is getting 10 points. Now, if that same page has 100 links on it, those links get only 1 point each, making them 90% less valuable. Of course, this is an over-simplification as I am certain that the actual formula is far more complicated, but I think you get the point. All other things being equal, the links you get are more valuable coming from a page with fewer other links, so these are the prime link building candidates for your site.
It should also be noted that even a site with a home page that has high page rank may have interior pages with much lower (even 0) page rank. Page rank is assigned for the page, not for the site, so when a page is added, it has a page rank of 0, and that rank may or may not ever increase. However, from my testing it does appear that a link from a site that contains some high-ranking pages performs better than links from those with low page rank pages, so I believe the overall page rank of the entire site does play some role in the ranking process, but I have no solid evidence to confirm this. With this information in mind, link building should not be limited to only pages with high page rank. Not only are these high page rank pages more difficult to use for link building, too many of then would produce an unnatural link building pattern that would likely be seen by Google as an attempt to manipulate the search results.
Link building is best within related content
The search engines are smart, and they are getting smarter every day. Google has the resources to attract and hire the best engineers on the planet, and these great minds have collectively worked for years to improve their search engine results. I have no doubt that they are well aware of all the methods used by people for link building, and it would seem logical that they would have in place some methods to determine whether a link is just randomly inserted on a page to get the benefit of a back-link, or whether the link fits within the context of the content which greatly increases the likelihood that it is a natural organic link.
Without diving into the complexities of what the Google secret algorithm may or may not look for, I think it is safe to assume they can easily associate one piece of content to another based upon the words on the page. For example, suppose your website is about fishing, and you are working at your link building plan by posting comments on other blogs, writing and submitting articles, etc. By scanning your site, the search engines know what your site is about because they detect many thematically related phrases like fishing, fishing tackle, bass fishing, catching fish, eating a fish sandwich, etc. You can go farther with this analysis by adding in more distant phrases that may still be related to fishing like camping, boating, going to the beach, water-sports, and hunting. You could imagine all these words on the same site, and maybe even the same page. So, when Google comes upon a link that points back to your site, and the page includes the words in the example above, it is easy to assume that the content may be related and a link back to your fishing site makes sense.
What about a link that was found on a page with words like perfume, flowers, candy-canes, Santa Claus, and televisions. It would be easy to see that the link back to your fishing site does not really “fit” the context of this page content, so it is out of place. While an out of context link is certainly possible, perhaps from a comment on a blog about an unrelated subject, it is a bit more suspicious. From experience with my own sites, any link is still a link, and it does have some value, however it is not too difficult to believe that within the complicated algorithm the search engines use to score your link building they would favor links from pages that were thematically related.
Yes, much of this is theory on my part, and no doubt there are many SEO link building experts that would take issue with this belief, it stands as not only logical but in keeping with the published guidelines that Google has released to guide webmasters with their link building and website promotion. Link building will always be an important ingredient, but it should be done with common-sense and with best practices in mind.
Avoiding the dreaded “no-follow” tag for link building
Many sites also attach the “no-follow” tag to external links so as to not dilute the page rank of their site. This tag is HTML code that tells the search engines not to follow this link, or to not transfer any authority through it. Without that tag, some of that page rank “juice” would flow through the link, slightly lowering the rank of the host page. While a few external links probably don’t make much difference, a page with many links could be seriously diminished by sharing their rank among many links.
A good example of this would be a popular blog post with hundreds of comments. Blog posts are extremely popular for link building, but if in each comment there was a regular link, that blog page would quickly dilute any power it may have had down to nothing. This is not good news for a webmaster, so most often the “no-follow” tag is assigned to all comment links. (There is no tag called a “follow” tag – all links are automatically “follow” unless the “no-follow” tag is present.)
Either way, with or without the “no-follow” tag, the link still has value to you as part of your link building campaign. If the “no-follow” tag is attached to the link, then you will still get the benefit of the link itself, but no page-rank or “juice” will flow with the link, making it worth a bit less than it might otherwise be worth. But a link is a link, and all links help to inflate your positioning in the search engine results.
The best practice for SEO Link Building is to obtain a mixture of regular and “no-follow” links because this combination of link growth looks more organic and natural. A page without any “no-follow” links pointing to it looks suspicious and may appear to be “gaming” the system. This could result in unwanted attention from the Google computers or even a manual review of your site to insure compliance with the Google webmaster guidelines. It’s easy to build back-links, so there is no good reason to take chances by employing black-hat link building methods that will eventually cause problems.