Solutions Used To Prevent Comment Spamming
The nofollow tag Google announced in early 2005 that hyperlinks with rel=”nofollow” attribute would not influence the link target's ranking in the search engine's index. The Yahoo and MSN search engines also respect this tag. ...
Original post: Solutions Used To Prevent Comment Spamming by at nofollow tag - Google Blog Search
Blog tag: Nofollow links
Technorati tag: Nofollow links