#23: Users will not read dialog boxes. Especially on Windows. They will click them away and not even realize they existed.

Try it.

1) Put a dialog popup in your MS desktop app that says, "Clicking OK below will destroy the chair beneath you. Clicking Cancel will make a box of chocolates appear on your desk."

2) Observe when a user performs a task that produces the pop up.

3)Ask the user if they were disappointed that no chocolate appeared.

The user will look at you with incomprehension.

To clarify, I am not criticizing users. Users are users, we're not going to change their behavior with training or help manuals. We need to design around them.