Nofollow is a link attrubute adopted by search engines like Google and Yahoo to fight comment and link spam. This nofollow link attribute is automatically added when you post a comment in any wordpress or blogger.com blogs. Recently wikipedia also introduced this nofollow link attribute to fight link spam.
Search Engine Journal came up with a post on how Google, Yahoo and others treat this nofollow link attribute. They have some interesting points about nofollow link attribute. Google wont follow that link and it wont give any attribution to the link. Yahoo will follow the link but it wont give any attribution to the link. In contrast Ask.com will follow the link and give attribution to that link because it has not yet supported the nofollow tag officially.
The nofollow links may not hold any value from Google, but from Yahoo and Ask.com thay do.
