If you're a blogger (or a blog reader), you're painfully familiar with people who try to raise their own websites' search engine rankings by submitting linked blog comments like Visit my discount pharmaceuticals site. This is called comment spam, we don't like it either, and we've been testing a new tag that blocks it. 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.
Google Blog ButtUgly