I wanted to squash a theory before it even gets out there, well, I may be a bit too late for that... As we know, Yahoo! Adds NOYDIR Support To Exclude Yahoo! Directory Titles in Yahoo! Search Results. And at the same time, there is a Global Yahoo! Search Index Update. But the two are not related.
The NOYDIR tag will have zero affect on your rankings.
Threads at both Search Engine Watch Forums and DigitalPoint Forums have some people thinking that the new rankings they see have to do with this tag. They do not.
Tim Mayer commented at Search Engine Watch Forums saying:
The ranking changes are due to the index update and have nothing to do with the NoYDIR tag launch.Tim
So if someone asks you, will it change my rankings. The answer is no.
Forum discussion at WebmasterWorld, Cre8asite Forums, Search Engine Watch Forums and DigitalPoint Forums