Yahoo introduced a robots-nocontent tag on the Yahoo! Search Blog. The new robots-nocontent tag allows you to note sections of a page, such as navigation, headers, boilerplate, legal disclaimers, etc. that you want Yahoo! to ignore. This allows the unique content to become the main focus of the page.
When Yahoo! comes to visit the page, it will not acknowledge the content/code within the robots-nocontent tags as useful information for finding the page for search results. Now, my concern is if someone places their navigation within this tag; isn't the navigation valuable information when it comes to finding a page? Doesn't your internal link structure play a role in your search results as well as anchor text used within the navigation links?
I caution those who choose the new robots-nocontent tag to use it wisely. The new tag can be a useful tool. Just be sure to put long consideration and thought into the decision before choosing to use the robots-nocontent tag on a section of your pages.