Many aspects are involved when you evaluate a link. As we just outlined, the most commonly understood ones are authority, relevance, trust, and the role of anchor text. However, other factors also come into play.
In the following subsections, we discuss some of the more important factors search engines consider when evaluating a link’s value.
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. Extending this notion a bit, it may be that you have multiple websites. Perhaps they have common data in the Whois records (such as the IP address or contact information). Search engines can use this type of signal to treat cross-links between those sites that are more like internal links than inbound links earned by merit.
Even if you have different Whois records for the websites but they all cross-link to each other, the search engines ...