Exactly one of these methods returns #t to indicate the type
of a given event, and the others return #f for the event.
Returns #t if the Alt key was pressed when the
event was generated, #f otherwise.
Returns #t if the Ctrl key was pressed when the
event was generated, #f otherwise. 
Returns a string indicating the tag of the HTML element where the
mouse is being moved from.  The return value is valid only for
events for which 
mouseover? or 
mouseout? produces 
#t.
Returns a string indicating the identifier of the HTML element where
the mouse is being moved from.  Return value is valid only for
events for which 
mouseover? or 
mouseout? produces 
#t.
Returns a string indicating the identifier of
the HTML element where the event occurred.
Returns a number indicating the keycode for the key that generated
the event.  Return value is valid only for events for which
keypress?, 
keydown?, or
keyup? produces 
#t.
Returns #t if the Shift key was pressed when the
event was generated, #f otherwise.
Returns a string indicating the HTML tag of the
element where the event occurred.
Returns a string indicating the tag of the target HTML element where
the mouse is being moved to.  Return value is valid only for events
for which 
mouseover? or 
mouseout? produces 
#t.
Returns a string indicating the identifier of the target HTML
element where the mouse is being moved from.  Return value is valid
only for events for which 
mouseover? or
mouseout? produces 
#t.
Returns an integer indicating the x-coordinate
within the document where the event occurred.
Returns an integer indicating the y-coordinate
within the document where the event occurred.