nnot contain the <code>img</code>, <code>object</code>,
<code>big</code>, <code>small</code>, <code>sub</code>, or <code>
sup</code> elements.</dd>

<dt><code class="tag">button</code></dt>
<dd>cannot contain the <code>input</code>, <code>select</code>,
<code>textarea</code>, <code>label</code>, <code>button</code>,
<code>form</code>, <code>fieldset</code>, <code>iframe</code> or
<code>isindex</code> elements.</dd>
<dt><code class="tag">label</code></dt>
<dd>cannot contain other <code class="tag">label</cod