The other day I prayed behind a Shi'a Muslim without realizing and I noticed a little later that he was Shi'a. The prayer I followed didn't seem like the usual prayer I normally follow behind Sunni Muslims. I didn't notice all the differences, but I was worried I, as a Sunni Muslim, hadn't completed my prayers 'properly.'
Do Sunnis find it acceptable to pray behind Shi'ites, or vice-versa? And is their salah accepted?