title: Placing border inside of div and not on its edge
body: <p>I have a <code>&lt;div&gt;</code> element and I want to put a border on it.  I know I can write <code>style="border: 1px solid black"</code>, but this adds 2px to either side of the div, which is not what I want.  </p>
  
  <p>I would rather have this border be -1px from the edge of the div. The div itself is 100px x 100px, and if I add a border, then I have to do some mathematics to make the border appear.</p>
  
  <p>Is there any way that I can make the border appear, and ensure the box will still be 100px (including the border)?</p>