Notification signs. In all zoning districts, the number, location, and size of legal notification signs erected by public agencies shall be in accordance with the laws of the commonwealth. In all zoning districts, legal notification signs posted on private property by property owners, such as "no trespassing," "no hunting" and the like, shall be limited to a surface area not exceeding two square feet. The placement and maximum number of signs permitted along road frontages shall be one sign for every 100 feet of road frontage.