Thanks for your prompt reply! No, I didn't sign into any social network. It's quite interesting, because my post should not have gotten out there. Here's what happened: 1. I typed the question and click "Publish"; 2. the web site asked me to sign in; 3. I thought "of course" and CLOSED THE BROWSER TAB; 4. in another browser tab, I then went to the sign-up page and created a new account; 5. I browsed the site a little, and tried to start a new thread for the question I really wanted to ask; 6. suddenly I was brought to this forum, and saw my post already been there. Is there a way to delete a post? Oh, and I'm not sure this text box is the right place to follow my thread. Please forgive me if I'm doing a stupid thing again.