Brave doing something you are afraid of doing but doing it anyway knowing the risk wont in danger your life.
Stupid is doing something you know can put your life in danger but you still go ahead and do it anyway :)
Brave people think about their actions, before they act. They know the risks and act anyway. Stupid people just act.. those are generally the ones you see on Cop Videos getting hit by a bus.
Stupid is when someone does something daring and it's preceded by the phrase "hold my beer."
Brave is for a good cause including thrills to the best of your ability with no guarantees but at least some chance of a good outcome..
Stupid is for no positive effect,without any basis in sound principles and without considering what might go wrong and being prepared for it.
Brave people do seemingly stupid things but are aware of the risks and can avoid them. Stupid people do seemingly brave things but in reality are just plain stupid. =P
It's the same as the difference between what is right and what is easy.
Brave would be doing something dangerous while KNOWING it is dangerous; stupid is doing something dangerous and not having the brains to know that it IS dangerous