Rel=”nofollow” can be used with the following syntax:
<a href=http://seomention.coml=”nofollow”>Search Engine Optimization</a>
Links can have lots of attributes applied to them, but the engines ignore nearly all of these, with the important exception of the rel=”nofollow” tag. In the example above, by adding the rel=”nofollow” attribute to the link tag, we’ve told the search engines that we, the site owners, do not want this link to be interpreted as the normal “editorial vote.” Nofollow came about as a method to help stop automated blog comment, guestbook, and link injection spam, but has morphed over time into a way of telling the engines to discount any link value that would ordinarily be passed. Links tagged with nofollow are interpreted slightly differently by each of the engines.
nofollowed links carry no weight or impact and are interpreted as HTML text (as though the link did not exist). Google’s representatives have said that they will not count those links in their link graph of the web at all.
Yahoo! & Bing
Both of these engines say that nofollowed links do not impact search results or rankings, but may be used by their crawlers as a way to discover new pages. That is to say that while not count them as a method for positively impacting rankings.
Ask is unique in its position, claiming that nofollowed links will not be treated any differently than any other kind of algorithms (based on local, rather than global popularity) are already immune to most of the problems that nofollow is intended to solve.