onmouseout, onmouseover | NN 2 IE 3 DOM 2
| Bubbles: Yes; Cancelable: Yes
Fire when the user rolls the mouse pointer into (onmouseover) or out of (onmouseout) an element's space (including border or padding, but not margin). Each event fires just once per entry and exit (except in Navigator 4 for Windows, in which the event fires repeatedly, similar to onmousemove).
Because the onmouseout event doesn't officially fire until another element in the window fires its onmouseover event (whether you have a handler for it or not), the onmouseout event may not fire if the target element is at the edge of a window or frame, and the user whisks the pointer outside of the current frame without the first frame's body element ever receiving the onmouseover event. If you use onmouseout events to restore image swaps, the user could see a stuck image. Leave sufficient space around your swappable images to account for this behavior.
An event object created from a mouse event has numerous properties filled with details such as coordinates of the click, the mouse button used, whether any modifier keys were held down during the event, and where the incoming pointer came from or outgoing pointer has gone. The event handler function can inspect these properties as needed.
Note that in Netscape 6, mouse events can fire on child text nodes of container-type elements, meaning that the event object's target property references the node, rather than the element. See Chapter 6 for details about the impact of this W3C DOM-endorsed behavior and cross-browser solutions.
Although these events have been supported in one form or another since the early days of scriptable browsers, only modern browsers can fire the event on virtually any other rendered element. For older browsers, the events were limited to a and area elements (where a elements surrounded images to be swapped).
Typical Targets
All rendered elements, except as noted above.