title: Percentage width for fixed elements?
body: <p>I have html like this:</p>
  
  <pre><code>&lt;div id='content'&gt;
      &lt;div id='first'&gt;...&lt;/div&gt;
      &lt;div id='second'&gt;...&lt;/div&gt;
  &lt;/div&gt;
  
  #content
  {
      width:100%;
      position:relative;
      padding:20px;
  }
  
  #first
  {
      width:70%;
      position:relative;
  }
  
  #second
  {
      width:70%;
      position:fixed;
  }
  </code></pre>
  
  <p>this causes the second div to be a bit wider (40px to be exact) than the first div, because the first div's 70% is with respect to the content's width (which is 100% minus the padding of 20px on each side).</p>
  
  <p>What does the second div's 70% refer to? How could I make it so that the two divs are the same width?</p>