Walking on your shadow is good or bad luck?

I always thought it was bad luck, but this website said it was good luck. I'm not as superstitious or anything, but I'm using it as an example of symbolism for a book and I want my facts straight.

was walking in the shadow of bad luck in antiquity it would not be able to see some creep up to you, and he was the victim of an attack

Was it luck or skill