1.在form create的时候要
Application.OnMessage := ApplicationMessage;
2.声明一个procedure
procedure ApplicationMessage(var Msg: TMsg; var Handled: Boolean);procedure tfrmhtmlbrowser.ApplicationMessage(var Msg: TMsg; var Handled: Boolean);
var
  wb: tembeddedwb;
begin
  WB := GetVisibleWebBrowser;//就是取当前webbrowser啦
  if (Msg.message = WM_CLOSE) and (Msg.hwnd = Wb.Handle) then //如果是当前                                                            //webbrowser关闭的话
  begin                                     
    closebtnclick(Self);
  end
  else
    inherited;
end; //end applicaitonmessage