The Nofollow Attribute
The new attribute is called "nofollow" with rel="nofollow" being the format inserted within an anchor tag. When added to any link, it will serve as a flag that the link has not been explicitly approved by the site owner.
For example, this is how the HTML markup for an ordinary link might look:
<a href="http://www.site.com/page.html">Visit My Page</a>
This is how the link would look after the nofollow attribute has been added, with the attribute portion shown in bold
<a href="http://www.site.com/page.html" rel="nofollow">Visit My Page</a>
This would also be acceptable, as order of elements within the anchor tag makes no difference:
<a rel="nofollow" href="http://www.site.com/page.html" >Visit My Page</a>
Once added, the search engines supporting the attribute will understand that the link has not been vetted in some way by the site owner. Think of it as a way to flag to them, "I didn't post this link -- someone else did."
If Google sees nofollow as part of a link, it will:
NOT follow through to that page.
NOT count the link in calculating PageRank link popularity scores.
NOT count the anchor text in determining what terms the page being linked to is relevant for.