Another security issue, mostly ignored, appears as a warning message that says something like "This site is not secure or the security certificate has expired. Do you want to go to the site anyway?" Many Internet users don't understand the message, and when it appears, they simply click Okay or Yes and go on with their work, unaware that they may be on quicksand. Be warned: On a Web site that does not use a secure protocol, you should never enter any confidential information such as your address or phone number, credit card or bank account numbers, or anything else you want to keep private.