The following special provisions shall be observed in the erection or placement of signs and outdoor advertising structure:
Signs and advertising structures where permitted shall be erected or placed in conformity with the side and rear yard requirements of the District in which located except that no sign or advertising structure shall be permitted within fifty (50) feet of the front, side or rear lot line of any lot in any "R" District or which faces any public parkway, public square or entrance to any public park, public or parochial school, library, church or similar institution and which is located within one hundred (100) feet thereof.