What are the Meta Tags ‘NOODP’ and ‘NOYDIR’ Used For in SEO?

Recently I came across a client who had <meta name=”robots” content=”NOYDIR” /> and <meta name=”robots” content=”NOODP” /> tags in their meta data and I feel there is need to go in depth on the purpose of these two tags and how they can affect SEO.   A while back we wrote on this topic when the new canonical tag came out. But it’s been a few months and I feel it’s important to highlight the two tags individually.
Let’s talk about NOODP first. According to Matt Cutts blog, in some cases, if someone types in a keyword into the search, Google may use descriptions from the open directory project as the page title and meta description for you organic listing.  The NOODP tag allows you to essentially opt out of the open directory project title and description override.  Just in case you weren’t aware, the open directory project is DMOZ.  Matt mentions that it may take 3 to 4 days for your NOODP meta tag to update after your page was re-crawled.
The benefits of using this meta tag is if you do have a DMOZ listing it is possible for a site to drop in page rank for specific keywords that are present in your specified page title and meta descriptions.  Matt says you may not notice a major difference in position, but enough for you to possibly lose a couple hundred visits.  Unfortunately the DMOZ listings can often use outdated, inaccurate or not very well written.
Now, the NOYDIR meta tag is specifically used to prevent the search engines from displaying your Yahoo! Directory page title and meta description.  This is used for all of the same reasons mentioned above, only it’s for Yahoo!.  SEOWorkers.com says that Yahoo!’s spider ‘slurp’ is the only spider that will use the Yahoo! Directory page title and meta description.
There are a few ways you can implement these tags for the search engines.
1.  You can add them in separately for DMOZ, Yahoo! Directory and even for MSN by using the three tags below according to SEOWorkers.com:

• If you only have the problem with Google, you can use this:

<meta name=”googlebot” content=”NOODP” />

• If you only have the problem with Yahoo!, you can use this:

<meta name=”slurp” content=”NOYDIR” />

• If you only have the problem with MSN, you can use this:

<meta name=”msnbot” content=”NOODP” />
2. Or for a quicker way to implement these tags, is to add one single line of code with multiple attributes separated by commas to exclude both the DMOZ and Yahoo! Directory from displaying their page titles and meta descriptions.

• <meta name=”robots” content=”NOODP,NOYDIR” />

So, if you ask yourself, when was the last time I looked at or updated my DMOZ or Yahoo! Directory page title and meta description? And the answer is never, you may just want to implement these tags to avoid allowing the search engines to use an older, outdated and possibly irrelevant title and description from these two sources.