title: Should setting `checkbox.checked = false` not clear the HTML attribute too?
body: <p>Here's my HTML:</p>
  
  <pre><code>&lt;input id="test" type="checkbox" checked=""&gt;
  </code></pre>
  
  <p>Here's a Firebug excerpt:</p>
  
  <pre><code>&gt;&gt;&gt; test
  &lt;input id="test" type="checkbox" checked=""&gt;
  
  &gt;&gt;&gt; test.checked = false
  false
  
  &gt;&gt;&gt; test
  &lt;input id="test" type="checkbox" checked=""&gt;
  </code></pre>
  
  <p>Um...am I missing something, or should that last line not read the following?</p>
  
  <pre><code>&lt;input id="test" type="checkbox"&gt;
  </code></pre>
  
  <p>UI-wise, the checkbox does indeed uncheck when I execute the <code>checked = false</code> line.</p>
  
  <p>Anyway, if there's some legitimate explanation for this, then what's the proper way to uncheck a checkbox from JavaScript, if not <code>checked = false</code>?</p>