No assessment, re-assessment, adjudication, review, revision, appeal, rectification, notice, summons or other proceedings done, accepted, made, issued, initiated, or purported to have been done, accepted, made, issued, initiated in pursuance of any of the provisions of this Act shall be invalid or deemed to be invalid merely by reason of any mistake, defect or omission therein, if such assessment, re-assessment, adjudication, review, revision, appeal, rectification, notice, summons or other proceedings are in substance and effect in conformity with or according to the intents, purposes and requirements of this Act or any existing law.