I want to know what is basic practices followed on the stack exchange if answer gets down-voted and some other users has provided satisfactory answer? In this case, should answer be deleted or left unchanged?
I wouldn't worry to much about a downvote now and then. Of course, it's always a good idea to consider what the reason might be and see it as an opportunity for improvement but sometimes there is nothing to be done. This question covers everything I can think of.