Section 1168. Certificate of sale as evidence

1. The certificate of sale or
  any   other   written  instrument  representing  a  tax  lien  shall  be
  presumptive evidence in all courts in all proceedings by and against the
  purchaser and his or her representatives,  heirs  and  assigns,  of  the
  truth  of  the  statements therein, of the title of the purchaser to the
  property therein described, and of the regularity and  validity  of  all
  proceedings had in reference to the taxes or other legal charges for the
  non-payment of which the tax lien was sold and the sale thereof.
    2.  After  two  years  from  the issuance of such certificate or other
  written instrument, no evidence shall be  admissible  in  any  court  to
  rebut  such  presumption  unless  the holder thereof shall have procured
  such certificate of sale or such other written instrument  by  fraud  or
  had previous knowledge that it was fraudulently made or procured.