Notwithstanding any provisions of this chapter to the contrary, all signs erected following the effective date of these regulations shall comply with all the provisions of these regulations when erected. All signs which are in existence on the effective date of these regulations that do not conform with the standards of this chapter, shall be considered nonconforming uses and shall be subject to the following provisions:
(a) No nonconforming sign shall have any changes made in the words or symbols used or the message displayed on the sign unless the sign is specifically designed for periodic change of message.
(b) No nonconforming sign shall be structurally altered so as to change the shape, size, type or design of the sign, nor shall any nonconforming sign be relocated.
(c) No nonconforming sign shall be allowed to remain after the use of land or building which has ceased by discontinuance or abandonment to which the sign relates.