Reverse ground/polarity is caused by an error in wiring and/or in older homes without ground wires and homes with a knob and tube electrical until. In the old days, the electricians did not have the knowledge of electrical science that is available today.
An example of reversed polarity would be having the neutral (white wire) hooked up to the hot terminal and the hot (black wire) to the neutral terminal. One of the signs to pay attention to is tripping circuits. Appliances such as microwaves, dishwashers, toasters, space heaters or refrigerators continually malfunction. Losing power can also be a signal of a problem. Most appliances now have cords with one blade wider than the other, the larger prong is neutral. This is to help prevent reverse polarity.
Solution to prevent this safety hazard is to not ignore tripping circuits or sparks and call a qualified, licensed and bonded electrician.