Irregularities in making assessments and returns thereof, in the equalization of assessments, and in the mode and manner of advertising the sale of any property shall not invalidate or affect the sale thereof when advertised and sold for delinquent city taxes and special assessments in a city of the primary class as provided by law, nor shall the sale of any real estate or any such tax or assessment be invalid on account of such real estate having been listed in the name of any other person than that of the rightful owner.