Fire when the user presses (onkeydown) and releases (onkeyup) a keyboard key. These two events fire on a focusable element or object for almost every key of the keyboard, including function and navigation keys. The instance of the event object for these events contains information about the key (not the character) pressed.  You cannot reliably inhibit critical Ctrl character sequences, but if you prevent the default action of the onkeypress event for a text form control, the character does not arrive at the text field.