Yahoo just implemented a new tag called “Robots-NoContent” where a focus to the main content and the right pages on webmasters site. An excerpt to http://www.ysearchblog.com/archives/000444.html

Applying the “class=robots-nocontent” Attribute:
Here are a few examples of how to apply this attribute for various uses and different syntax options:

This is the navigational menu of the site and is common on all pages. It contains many terms and keywords not related to this site

This is the site header that is present on all pages of the site and is not related to any particular page

This is a boilerplate legal disclaimer required on each page of the site

This is a section where ads are displayed on the page. Words that show up in ads may be entirely unrelated to the page contents

This just indicates parts of the site that is not relevant or not important to the main site point of interest. Also in this implementation, yahoo also updating its search results including this addition on sites ranking.