Yahoo's new robots-nocontent attribute

Yahoo! announced yesterday via the Yahoo! Search Blog that they've introduced a class of robots-nocontent that you can add to sections of your pages to designate those “parts of a page that do not relate to the main content, such as navigation, menus repeated across the entire site, boilerplate text, or even advertising.”

The blog post gives examples, such as using this new functionality to mark required legal disclaimers, ads and/or a site-wide generic page header.

While they do say that links within sections set apart by the “robots-nocontent” class will be followed, I question the wisdom of using it to mark the site navigation. Since they also say they won't use content tagged with this class as “information for finding the page,” I'm concerned that this would exclude the anchor text of those internal navigation links from being considered toward page relevance. Depending on how your internal navigation is set up, this might or might not be a good thing.

Over at googlesystem.blogspot.com, they make the point that this is kinda the search engines' job to figure out what parts of the page content/code are important for ranking and which are not. On the other hand, the engines do make mistakes sometimes — not always recognizing as important what we think is important. Personally, I welcome the ability to give at least one of them some guidance to help them get it right.

My opinion: you'll want to be careful with how you use this, to ensure you don't accidentally prevent relevant content from being used as information to help find the page in Yahoo!, but on the whole this is A Good Thing.

So, now the questions are: Should the other major search engines follow suit? Will they? If so, will they use the same designation as Yahoo!, or will we have to learn a new syntax for each? And how many of us plan to actually use this new facility to mark portions of our page content?