Most milk should be stored in the main section of the fridge, where it will stay cold enough to remain fresh. The door of the fridge is generally the warmest part, so it's not ideal for storing milk. If you have a lot of milk and space is an issue, you can store some in the door compartment, but use it first. If you have raw milk, it should be stored in the back of the fridge, where it will be the coldest.