The Art of SEO, 2nd Edition

Further Refining How Search Engines Judge Links

Many aspects are involved in evaluating a link. As we just outlined, the most commonly understood ones are authority, relevance, trust, and anchor text. However, other factors also come into play.

Additional Link Evaluation Criteria

In the following subsections, we discuss some of the more important additional factors search engines consider when evaluating a link’s value.

Source independence

A link from your own site back to your own site is, of course, not an independent editorial vote for your site. Put another way, the search engines assume that you will vouch for your own site.

Think about your site as having an accumulated total link juice based on all the links it has received from third-party websites, and your internal linking structure as the way you allocate that juice to pages on your site. Your internal linking structure is incredibly important, but it does little if anything to build the total link juice of your site.

In contrast, links from a truly independent source carry much more weight. Suppose you have multiple websites. You might think that linking from one to another would be a good way of boosting its link juice, but in fact the search engines are pretty good at determining that the two sites are related. Perhaps they have common data in the Whois records (such as the same servers or contact information). Search engines can use this type of signal to treat cross-links between those sites more like internal links than ...