title: CSS set element max-width to body width minus x
body: <p>I have an <code>img</code> attribute in my HTML. I would like for the <code>max-width</code> of this element to be equal to the width of the body minus a number, say 60.</p>
  
  <p>How would I do this? I've tried this:</p>
  
  <pre><code>img
  {
      max-width:body.width - 60;
  }
  </code></pre>
  
  <p>But it seems that the element width is set to 60 instead.</p>
  
  <p>Any suggestions?</p>