Except as otherwise herein provided, all billboards and/or sign messages shall be removed by the owner or lessee of the premises upon which an off-premises sign/billboard is located when the business advertised is no longer conducted where advertised. If the owner or lessee fails to remove the sign/billboard, the Common Council shall give the owner 60 days' written notice to remove said sign/billboard and, thereafter, upon the owner's or lessee's failure to comply, may remove such sign/billboard, any costs for which shall be charged to the owner of the property or may be assessed as a special assessment against the property, and/or the Common Council may take any other appropriate legal action necessary to attain compliance.