Every business gets a critical review or two in their lifetimes. Maybe the review is true, or maybe you got a customer who lied. It sadly happens, but the more positive reviews you get should outweigh the really bad ones. With that being said though, have you ever responded to a critical review? How did that go for you? If you have the proof to back up your response, more power to you, but sometimes you can't prove a customer was right or wrong. It's all a matter of how you get over that review.