Usability for Nerds/Never interrupt the user
Ms Tippy is a fast touch typist. Right now she is typing a letter from a dictaphone. Suddenly a box pops up on her screen saying:
Ms Tippy doesn't see the message box because her eyes are at the dictaphone. Her next keystroke is a space, which activates the Yes button and opens her mail program. The rest of her keystrokes go to the mail program where they cause all kinds of funny (or perhaps not so funny) things to happen.
Even if Ms Tippy had been looking at the screen, she may have typed several keys in the few seconds it takes to recognize the new situation. These keystrokes could easily cause the message box to close before she had the time to read what it said.
An unexpected pop-up box is a serious usability error for several reasons:
- It breaks the system's predictability because the unexpected change of focus from the typing window to the message box radically changes what the keys do.
- It violates the principle that the user should be in control.
- It breaks the user's line of thought and steals the user's attention while they may be concentrating on something important.
This rule is important. Never interrupt the user!
An unprompted change of focus from one window to another should always be avoided. A big sinner in this respect is automatic software updates. Even big software companies that have large usability departments violate this rule with importunate pop-up windows telling the user that an "important" software update is available. I have even seen the Windows operating system updating automatically and restarting the system without user confirmation whereby the ongoing downloading of a big file was spoiled:
Time and attention are precious resources to many software users. Stealing those resources is a sign of disrespect to the user's work situation.
Messages to the user about new mail, new software updates, or whatever, should be presented discreetly as an icon in a corner of the screen. Sound, animations, or popup windows are completely unacceptable unless the message is very urgent, and even small popup messages can be disturbing.