Originally Posted by swami

But if your site has been up 12 months then its most likely a penalty of some sort.Quite possibly a duplicate penalty issue.Check to see that there is only one version of your site and that includes your www. version as well as the root version.If there are links from other sites to both the root domain and the www alias then this can cause problems unless you have a 301 redirect from one to the other.
Also make sure noone has copied your site.Other than that it could be a link penalty where yahoo thinks you have a link farm or that you are associated with a penalised site.