Santa's naughty or nice list documents the behavior of children and whether or not he delivers presents to them on Christmas. Children who end up on the naughty list can expect to receive coal in their stockings.
There are some websites where children can find out where they stand on Santa's naughty or nice list. The North Pole Times offers a tool children can use to enter their name and see what they can improve on to get better presents. Santa's Nice-o-Meter also lets children enter their name and see if they are super nice, nice, 'sorta' nice or not nice at all.