Myths and Superstitions, Omens?

Just for curisoity. Last night around 12am. I heard what sounded like two cats crying on the side of my house. Then heard one of them scratching up against my house and when I looked out it was a black cat walking the outline of my porch. In scottland I heard that if a black cat is on your porch it represents prosperity but then what if I seen it from behind is that a good omen. I was thinking about it today and wondered what it meant in different cultures and religions?