title: xHTML/CSS: How to make inner div get 100% width - margins
body: <p>I have 2 nested divs and outer one has width:100%</p>
  
  <pre><code>&lt;div id="#outer" style="width:100%; border:1px"&gt;
    &lt;div id="#inner" style="width:100%; border:1px; margin:4px"&gt;
      something inside ...
    &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>But in this case inner div exceeds width of outer by 8px (margins).
  How to make inner div to get width of outer div minus 8px margin?</p>
  
  <p>P.S. All styles are in separate classes in my case, here I putted CSS into style attributes just for simplification.</p>