Help information needs to be readily accessible and just as readily removable. An undo function supports learning by trial and error by minimizing the cost of errors. An undo function allows the user to retract previous actions, and fosters a spirit of exploration and experimentation that is essential. Use Explicit Destruction Explicit destruction means that, when an action has irreversible negative consequences, it should require the user to take an explicit action to perform it. Warnings protect the user from inadvertent destructive operations, yet allow the user to remain in control of the application.
Warnings also encourage the user to experiment without fear of loss.
Operations that can cause a serious or unrecoverable loss of data should warn the user of the consequences and request explicit confirmation.