The Managed Document Object Model (DOM) exposes only a select number of events. Most of the unexposed events are only defined for specific types of elements; such as the submit event, which is valid only on FORM elements. Use HtmlElement.AttachEventHandler(string, EventHandler) to add an event handler to these unexposed events.
You should not attach an event to the document or one of its objects until the document has completed loading. The earliest you should call this method is in the WebBrowser.DocumentCompleted event of the System.Windows.Forms.WebBrowser control.
For more information about the available unmanaged events, see Accessing Unexposed Members on the Managed HTML Document Object Model and the IHTMLElement interfaces: tp://go.microsoft.com/fwlink/?LinkId=104876, tp://go.microsoft.com/fwlink/?LinkId=104877, tp://go.microsoft.com/fwlink/?LinkId=104878, tp://go.microsoft.com/fwlink/?LinkId=104879.