Preventing Comment Spam : “From now on, when Google sees the attribute (rel=”nofollow”) on hyperlinks, those links won’t get any credit when we rank websites in our search results. This isn’t a negative vote for the site where the comment was posted; it’s just a way to make sure that spammers get no benefit from abusing public areas like blog comments, trackbacks, and referrer lists.
We hope the web software community will quickly adopt this attribute and we’re pleased that a number of blog software makers have already signed on:“
So we can have control semantics, I guess it depends who makes them ….
“We’ve also discussed this issue with colleagues at our fellow search engines and would like to thank MSN Search and Yahoo! for supporting this initiative. Here are a few guidelines for anyone else who wants to join the cause. “
Surprising to see Microsoft and Yahoo agree with Google’s rules.