1. The house on the eighth floor is not good.
2. geomantic omen is unlucky: some people who believe in geomantic omen think the eighth floor is unlucky.
The 3rd and 8th floors are unlucky: for example, it's messy, upside down, falling apart, conflicting views, seven-seven-eight-eight, seven-eight-fold, seven-eight-fold, seven-eight-fold, seven-eight-fold, seven-eight-fold, eight-eight-fold, eighteen-storey hell, etc.