Since Internet Explorer 4.0x doesn't feature a captureEvents() method to capture events at a high level, it doesn't feature the releaseEvents() method to stop capturing the events. Therefore, the only way to disable an event handler is to completely delete it. For example, the following statement specifies an onclick event handler for the document object:

document.onclick = functionName;

while the following statement disables the event handler:

document.onclick = null;

Once you assign null to the event handler property, it does not have any function to process an event that comes its way. In other words, the null value disables the object's event handler.

Note that this technique is also supported in Navigator. It can be used for any object, and for any event handler.