falls Google das nutzt, ist es sicherlich eine mögliche Erklärung.
"The "rel" attribute
As of 18th January 2005, Google, together with other search engines, is
recognising a new attribute to the anchor tag. The attribute is "rel",
and it is used as follows:-
<a href="http://www.domain.com/somepage.html" rel="nofollow">link text</a>
The attribute tells Google to ignore the link completely. The link won't
help the target page's PageRank, and it won't help its rankings. It is
as though the link doesn't exist. With this attribute, there is no
longer any need for javascript, forms, or any other method of hiding
links from Google."