A rel="" attribute is desirable for links, for example to

* limit the interest of comment spam with rel="nofollow" for anonymous wiki contributions (see [Google](http://googleblog.blogspot.com/2005/01/preventing-comment-spam.html))
* identify page tags with rel="tag" (see [microformats](http://microformats.org/wiki/rel-tag))
* define a social network with rel="friend co-worker met ..." for contacts (see [XFN](http://www.gmpg.org/xfn/))
* define a license with rel="license" (see [microformats](http://microformats.org/wiki/rel-license))

This patch adds this possibility to htmllink().

This one uses it for tags:

> Both applied, thanks. Leaving the bug open since other parts are not
> implemented yet. See also [[rel=nofollow_on_external_links]] --[[Joey]]

This can also help for css decoraton. An example of these patches in use: http://poivron.org/~nil/iki/japonesie/horizon_large/

— NicolasLimare

[[!tag wishlist]]
