Yahoo SERP getting complex

I want clarification for quite a few queries that are interrelated, so please give suitable answers to all the queries in brief. I feel it is better to ask one query rather than creating individual post for each query. Why does Yahoo SERP behave so strangely? I get shocking results for my site and there is no explanation for such weirdness. Can anyone help me in finding the cause of such behavior or ways of controlling such behavior? Yahoo SERP is getting more and more complex with time, which is making it more difficult to understand it. Has anyone of you had any similar experiences with yahoo?