All list of values for HTML rel attribute

Question

I would like to know more on rel attribute used with a html elements. Does anyone know some list of attributes useful for SEO and social?

<a title="" rel="friend met neighbor" href="#">This is a link</a>

I know it only inside WordPress and it's links manager, but nothing more.

Answer 1

HTML5 defines some values for the rel attribute: http://www.w3.org/TR/html5/links.html#linkTypes

For the use in HTML5, all other link types need to be defined/listed on this page in the microformats wiki: http://microformats.org/wiki/existing-rel-values#HTML5_link_type_extensions