In fact, in DHTML, it can be said that this mechanism to be entrusted very early.
The events in .NET ( =, - =) and DHTML (Attachevent, Detachevent) are the same (personal understanding)
Object.attachevent (fpNotify) is equivalent to Object.Event = EventHandler (FPNOTIFY)
Object.detachevent (FPNOTIFY) is equivalent to Object.Event - = EventHandler (FPNOTIFY)
