Firefox 3 adds two new events that allow you to determine when drag operations begin and end. These events are new in the current working draft of the HTML 5 specification.
Note: The drag and drop event support advertised in the Firefox 3 release notes is not the same as the events described in the Drag and drop section of the HTML 5 working draft. E.g. Firefox 3 does not support the 'drag' event. This support is added in Firefox 3.5, and is documented separately on the page [Drag and Drop].
drag- Sent when a drag operation begins.
dragend- Sent when a drag operation ends.
For more information about drag and drop, see the article Drag and Drop.
You can see an example of these events in action here: