Error Messages: You failed, stupid!

I once got into a 5 minute debate (which was 4 minutes and 30 seconds too long) about error messages. The other person felt that error messages should make the user feel good about themselves. In other words, never tell the user that they have failed nor use negative imagery, such as, the color red. Their example was, "how would you feel if you failed a medical test?" I could not disagree more. Most people are not insulted by machinery. People are more likely to be insulted by poorly designed products and confusing instructions. A well written error message includes two things: 1. A general statement defining the error condition. 2. Specific instructions on how to fix the problem. The user doesn't need to know exactly what went wrong. If you get on the wrong freeway in your rental car, do you want your GPS to give you updated directions or tell you that you made the wrong turn on Albuquerque Street? Exactly. Who cares what the street was? You need to get to your conference in 10 minutes, not you don't need a lesson in modern city planning. Error message should be short, but informative. If your message takes more than two sentences, you should break the information into two or more error conditions. And as always, protect the user experience.