CSS height property doesn't work with %

[Incompetnce]

I don't understand why the height property doesn't work percentages. And min-height doesn't work at all. This is in firefox. I don't understand it at all. Is there something I'm missing? Do the properties have to be in a certain order?

[r2d2]

What are you trying to apply a height to?

[Incompetnce]

im trying to apply height to a div element.