1. First, if you have a link (anchor), just add an attribute "rel on it.
2. The value of attributes are as follows (reference: http://gmpg.org/xfn/join)
<a href="http://mypartnersite.com/" rel="acquantance met co-worker">text for my co-worker site</a>
|relationship category||XFN values|
|friendship (at most one):|
|geographical (at most one):|
|family (at most one):|
3. Then, at your head tag, you must reference the XFN profile by adding an attribute "profile" and giving it a value of "http://gmpg.org/xfn/11" . and that's it.
< head profile="http://gmpg.org/xfn/11" >
I'm just thinking that doing this will improve the Web 3.0 - Semantic Web, since it will have something to check whether sites are in what way related or not. That, I'll have to find out and see what happen next. ^_^