In the Microsoft model you must set the event’s cancelBubble property to true.
window.event.cancelBubble = true;
In the W3C model you must call the event’s stopPropagation() method.
event.stopPropagation();
Here’s a cross-browser solution if you’re not using a framework:
function doSomething(e) {
if (!e) e = window.event;
e.cancelBubble = true;
if (e.stopPropagation) e.stopPropagation();
}