All signboards and billboards shall be securely anchored or fastened so as to be safe and secure. Except as may be otherwise provided in the Zoning Code, signboards and billboards, other than those painted and erected upon a building, shall be limited to twelve feet by twenty-five feet and shall not be located nearer than twenty-five feet behind the front line of the lot whereupon the same are erected or nearer than twenty-five feet from any building.