255. Every notice which, by or under this Act, is to be given or served as a public notice or as a notice which is not required to be given to any individual therein specified shall, save as otherwise expressly provided, be deemed to have been sufficiently given or served if a copy thereof is affixed in such conspicuous part of the office of the Board or in such other public place, during such period, or is published in such local newspaper or in such other manner, as the Board may direct.