temanhsu Hi. I think this thread is a duplication of the same question, but since I'm not able to find it right now. I'll answer again. If I'm not wrong and there are 2 threads about the same issue You've started please do not reply to one of them.
You have a module published in "mainbody" module position. This method is used to replace component loaded on page. Simply move any module published in "mainbody" to a different module position.