Yahoo introduced a new class for unrelated content on websites like header, footer and navigational links. Webmasters have to add “robots-nocontent” as a CSS class tag to <div>, <span> or <p> in their pages, this will tell Yahoo crawler that the information in this part is unrelated to the main content.
Excerpts from Yahoo Search Blog
This tag is really about our crawler focusing on the main content of your page and targeting the right pages on your site for specific search queries. Since a particular source is limited to the number of times it appears in the top ten, it’s important that the proper matching and targeting occur in order to increase both the traffic as well as the conversion on your site. It also improves the abstracts for your pages in results by omitting unrelated text from search result summaries.
To do this, webmasters can now mark parts of a page with a ‘robots-nocontent’ tag which will indicate to our crawler what parts of a page are unrelated to the main content and are only useful for visitors. We won’t use the terms contained in these special tagged sections as information for finding the page or for the abstract in the search results.
Last time when “nofollow” tag was added major search engines supported the move and it became useful to fight link spam, now this time it is only Yahoo who is introducing this tag. I am not sure how Google handles this unrelated content, if Google can handle it without adding a tag then Yahoo should be able to do it.
How to add this tag:
Some examples on how to add this class attribute
<div class=”robots-nocontent”>unrelated content goes here</div>
<span class=”robots-nocontent”>unrelated content goes here</span>
<p class=”robots-nocontent”>unrelated content goes here</p>
<div class=”robots-nocontent”>unrelated content goes here</div>