return NS_ERROR_NOT_IMPLEMENTED;
nsCStringKey key(prop); if (Exists(&key)) return NS_ERROR_FAILURE;  nsISupports* prevValue = (nsISupports*)Put(&key, initialValue); NS_ASSERTION(prevValue == NULL, "hashtable error"); NS_IF_ADDREF(initialValue); return NS_OK;
nsPersistentProperties::DefineProperty(const char* prop, nsISupports* initialValue){  return NS_ERROR_NOT_IMPLEMENTED;}