Split margins 1 to 3

固定幅の要素の余白をcalc()を使って1:3に分ける。

width: 320px

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nam consectetur lacinia arcu, vitae vulputate mauris elementum quis.

width: 480px

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nam consectetur lacinia arcu, vitae vulputate mauris elementum quis.