Including border and margin.
I thought I read a nice, correct way to do this but I can not find it
today when I actualy want to do this.
Can you define a total width of a container, including margin, border,
padding and content to be 50% as well as define a margin and border to
inside of that without resorting to a fixed width (i.e. 123px) or a
secondary container for the width?
