When you do, cardio depends on what you're looking to do. Before is great for weight loss and cardio health but not muscle growth and after a weight workout is great for muscle growth but hard for cardio fitness.
Weight training should come after cardio as you will be warmed up and stretched. This will make you less likely to injure yourself. You should then do light cardio to cool down after the weight training as well to prevent cramping and soreness.