There has been something very strange going on for the past few months:
I have websites ranking good on Yahoo, and not so good on Google, due to age factors mostly. But every time one of those websites breaks into the top 100 on Google - it takes an extreme dive on Yahoo - usually about 200 spots. No Yahoo updates, or links and no content chages most of the time. And I have a pool of over 30 different sites - it's just like Yahoo searches Google for the top 100s and if it finds a site of mine - it kicks it in the sack.
I have the same problem. One site ranked very well in Yahoo last year but not good in Google because it was new. Then, it started to rank well in Google but the ranking in Yahoo has dropped considerably.
I added Google Adsense to the site last year, about the time my ranking in Google started to improve, so I wonder if it is because of the adsense, i.e. Yahoo punish websites with Google Adsense?
I have always ranked well in Google and ranked well in Yahoo but was low on MSN. Then recently I moved up to #1 on MSN and dropped to the 3rd page on Yahooo. Now #1 and #2 on Google and MSN, 26 on Yahoo. No major changes. Not a particularly competitive area.