Any owner, part owner, tenant or lessee on whose property a sign is pasted shall be deemed to have knowledge of the erection and nature of the sign. Whenever the removal of any sign has been duly and legally ordered by the Zoning Administrator, the person, firm or corporation on whose premises such sign is displayed shall remove the sign within forty-eight hours after receiving such notice. Upon failure to remove, the Zoning Administrator may remove or cause to be removed such sign at the expense of the person, firm or corporation on whose premises it was erected, affixed or attached and each such person, firm or corporation on whose premises it was erected, affixed or attached shall be individually and separately liable for the expenses incurred in the removal of the sign.