I received an email. The sender blamed on me for my policy to guest's posting. Yes, allowing the guest posting can bring some convenience to the people who post. However, it causes tons of confusion to other people. Because there is no "session tracking" between us and the guest, I often need to judge which guest I am talking to now. Sometimes, I don't understand the guest's posting because he refers to his earlier posting. If you want to post anything serious, please do not use the guest identity. Thank you for your co-operation.