On Monday I wrote about Technorati’s use of the a element’s rel attribute to let people link weblog entries to taxonomy entries. I mentioned that this attribute, which was designed to implement link typing, has been all but ignored in its twelve-year history, and that its use by a big-time application would give people more incentive to use it.
Yesterday one of the biggest applications of all announced a use for the same attribute. To fight the practice of referrer spam (the addition of irrelevant comments to a weblog entry in order to boost the number of links to the spammer’s site), Google has announced that a rel value of “nofollow” on a link will tell their crawlers not to consider this link when calculating the link destination’s page rank. Several weblog applications have already updated their software so that links added in comments by weblog readers will automatically include this attribute setting. This gives perpetrators of referrer spam much less incentive to do add these worthless comments.
Comments added to my post of Monday (the good kind, not the spam kind) led to a discussion of how allowing people to add data and metadata to web pages that they don’t own leads to abuse, and whether the potential abuse renders user-added metadata features useless. This has always been Google’s justification for ignoring metadata, so it’s nice to see them encouraging the use of link metadata. (It was tempting to title this posting “Newsflash: Google crawlers paying attention to an attribute value besides href!”) They get extra credit for doing this with an attribute that’s been around for so long, instead of making up a new one, which is what many companies would have done.