Yahoo announced support for a new meta tag called "NOYDIR"

What is the new NOYDIR tag?

Yahoo, Google and other search engines often use the title and the abstracts that are used in Open Directory Project (ODP) listings or in Yahoo Directory listings for their search result lists.
Unfortunately, the titles and the descriptions that are used in these directories are often not the titles and descriptions that webmasters want to see in the search results.
The reason for that is that the editors of the directory assign the titles and the descriptions to the listed web sites and not the webmasters of the sites. Editors often see web sites differently than webmasters do.
In addition, these directory descriptions often become outdated and it is very difficult to change the title and the description of a web site in a big directory.
As many webmasters didn't like the ODP directory title and description in the search results on Google and other search engines, search engines invented the NOODP tag.
If the NOODP tag is used on a web page, search engines won't use the title and the description of the Open Directory Project entry for that web page. Yahoo now did the same with the NOYDIR tag.

How can you add the new tag to your web pages?

Just add the following code to the <HEAD> section of your web pages:
<META NAME="ROBOTS" CONTENT="NOYDIR">

If you insert that code snippet on your web pages then Yahoo won't use its directory description for your web site in the organic search results. If you also don't want that the Open Directory Project description is used for your web site, insert the following in the <HEAD> section of your web pages:
<META NAME="ROBOTS" CONTENT="NOODP">

How will the new tag influence your rankings on Yahoo?

If you use the new tag on your web pages than Yahoo will use the title of your web pages in its search results. The description will be created based on the content of the displayed web page.
Yahoo might still use the Open Directory Description so it is better to include both tags on your pages if you don't like your directory descriptions:
<META NAME="ROBOTS" CONTENT="NOODP, NOYDIR ">
The NOYDIR tag does not mean that the link from the Yahoo directory won't be considered in link popularity calculations. A link from the Yahoo directory to your web site will still have a positive effect on the link popularity of your web site.