sit + down

Question
One question.. I've been teaching my dog to sit and then down, but now whenever I say sit he goes down... how do i fix this (if i need to)?

Answer
He has simply learned a "behavior chain" instead of the discrete behavior that you wanted him to learn.  Probably you have a smart dog, and your timing was just a bit off when you rewarded him initially.  

When you say "sit" and he goes down, just step a little toward him and gently shuffle your feet against his toes.  As soon as he pops back into the sit, say "sit" as you reward.