Jacek Caban (@jacek) commented about dlls/mshtml/mshtml_private_iface.idl:
HRESULT classList([retval, out] IDispatch **class_list);}
+const long DISPID_IWINEHTMLFORMPRIVATE_NOVALIDATE = 51; +const long DISPID_IWINEHTMLFORMPRIVATE_CHECKVALIDITY = 52;
What's special about those ids?