Signs hereinafter designated shall be prohibited in all zoning districts.
1. Obsolete signs. Such signs that advertise an activity, business, product, or service no longer conducted on the premises on which the sign is located. In the case of off-premises or billboard signs they shall be declared obsolete if the activity, business, product, or service is no longer being conducted at the location being advertised.
2. Portable signs. Such signs that are not permanently anchored or secured to either a building or the ground except as may otherwise be permitted by this chapter pursuant to a temporary permit.
3. Off-premises signs on public property. Off-premises signs located on public property which is being used for public purposes.