Section 163. Assessment not invalidated by irregularities

No assessment or
  tax shall  be  vacated,  set  aside,  canceled,  annulled,  reviewed  or
  otherwise  questioned  or  affected  by  reason  of any error, omission,
  irregularity or defect, not actually fraudulent, in any of the steps  or
  proceedings  required  to  be  had or taken as preliminary to, or in the
  making of, the assessment, or in the levying or collection of  the  tax,
  nor  in  relation  to or in connection with any proposal, designation of
  materials, contract, work or improvement for or on account of which such
  assessment was made or tax imposed. But all property shall be liable  to
  assessment  and  all  assessments  shall  be valid and of full force and
  effect notwithstanding any such error, omission, irregularity or defect.