It would be useful to have a little pop-up window come up when students press the start button for a quiz asking them "are you sure you want to start?" It should warn them that the timer will start counting down and there is no turning back once they enter the quiz. Many students inadvertently open the quiz thinking they can close the quiz and restart it at any time, only to be shocked that the timer has run out later. It puts instructors in an awkward position when trying to decide how to handle these mistakes (make them take the low grade? give them a second chance that other students don't get?).