> You see, a box (the rectangular space taken up by an element) has several measurements: its own width and height, then surrounding whitespace called padding,

> You see, a box (the rectangular space taken up by an element) has several measurements: its own width and height, then surrounding whitespace called padding, then an optional border, then a margin separating it from neighboring boxes. CSS specifies that these properties are all additive. I never understood why CSS picked the obviously wrong way to define the box model. Who in their right mind would ever think that "width" would refer to the inner width of a box? I'm glad they finally added box-model: border-box, but the fact that there needed to be a switch at all is ridiculous.