Banner signs advertising a business or sale at a commercial business, which shall not exceed 25 square feet, shall be allowed to be installed once every six months, for a duration of 30 continuous days, after which time the banner sign shall be removed. Banner signs shall be those signs made of canvas, plastic, cloth, mesh, or similar materials. A sign may only be erected one for every 150 feet of frontage on a public road, alley or parking lot.