Many website pages will have a section like the one pictured to the right in the Wiki section. If not, you can add this section too by copying the formatting below into the page's wiki section.
In the wiki text this section is formatted like this:
==Related Domains== <WikiPages> AboutUs.org Google.com </WikiPages>
The words between the <WikiPages> </WikiPages> automatically get linked to the domain page for that website. The pages need to be in the format of AboutUs.org or Google.com to be properly linked (e.g. no "www", "http" or "/"s) and each on their own line.
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If you have a site that is related to a given topic, feel free to add some related links from other site pages to your page. Please don't over do it, however. If you're adding more than 20 such links or you're putting up links on very popular and not directly related sites, then you're overdoing it and it will look like spam.
The Related Domains area of each domain page uses this internal linking idea to create a "light rail" system which allows users to discover related sites. Ideally, each domain page would have somewhere between a few and no more than 20 related links.