return NS_ERROR_NOT_IMPLEMENTED;
if (mIsDone) return NS_ERROR_FAILURE; if (!mCurNode) return NS_OK; if (mCurNode == mFirst) { mIsDone = PR_TRUE; return NS_ERROR_FAILURE; }  return PrevNode(&mCurNode);
nsresult nsContentIterator::Prev(){  return NS_ERROR_NOT_IMPLEMENTED;}