title: Why does fixed positioning alter the width of an element?
body: <p>I have a <code>&lt;div&gt;</code> that has its width set as <code>100%</code>. When I add <code>position:fixed</code> to it, the width becomes <code>16px</code> larger.</p>
  
  <p>I noticed that on the body, there are <code>8px</code> margins on all sides, so I am guessing that <code>position:fixed</code> is somehow ignoring the margins of the body tag in which it is contained.</p>
  
  <p>I looked at the <a href="https://developer.mozilla.org/en-US/docs/CSS/position" rel="noreferrer">MDN Reference</a> but was unable to find anything that explains what is going on.</p>
  
  <p><strong>What has <code>position:fixed</code> changed about the <code>&lt;div&gt;</code> that causes this behavior?</strong></p>
  
  <p>Example: <a href="http://jsfiddle.net/UpeXV/" rel="noreferrer">http://jsfiddle.net/UpeXV/</a></p>