Temporary signs not exceeding fifty square feet in area, announcing special public or institutional events, the erection of a building, the architect, the builders or contractors may be erected for a period of sixty days plus the construction period. Such temporary signs shall conform to the general requirements listed in Section 1173.03, the setback requirements in Sections 1173.12 to 1173.15 and in addition, such other standards deemed necessary to accomplish the intent of this chapter as stated in Section 1173.01.