Maybe, some other sites just overtaken yours. So many webmasters here know the trick and kick hard with the techniques to get top spot.
Yes, yahoo has definately changed the way you find yourself ranked. Seems they favor people that don't even belong on the first page these days. Lots of people I know are finding themselves not listed on the first page anymore.
I wouldn't worry too much about the Yahoo or Google. Search engines can be so fickle. If you were able to get on the first page of either search engine, be certain that you can do it again. Don't give up, that's the important thing. Carmen
Yahoo rank up and down quite frequent when they doing some updating. This is back to normal after a week
One of my sites was ranking good in Yahoo - actually Number 1 for a very competitive keyword but nothing seems last for long with Yahoo - besides if you keyword is in the domain...