Comment spam is one of the banes of weblogs. Spammers use the high Google rank of weblog entries to boost their own rank. They waste resources, abuse the system, and interfere with regular people trying to communicate with one another.

Six Apart, Google, Yahoo Search and MSN Search have worked together to develop a new link attribute, nofollow:

The search team at Google approached us with the idea of flagging hyperlinks with a rel="nofollow" link attribute in order to alert their search spider that a particular link shouldn’t be factored into their PageRank calculations. The Yahoo and MSN search teams have also indicated they’d support this new spec, and we’ll be implementing and deploying this specification as quickly as possible across all of our platforms around the world.