title: CSS :after not adding content to certain elements
body: <p>I'm having trouble understanding the behavior of the CSS <code>:after</code> property. According to the spec (<a href="http://www.w3.org/TR/CSS21/selector.html#before-and-after">here</a> and <a href="http://www.w3.org/TR/CSS21/generate.html#before-after-content">here</a>):</p>
  
  <blockquote>
    <p>As their names indicate, the <code>:before</code> and <code>:after</code> pseudo-elements specify the location of content before and after an element's document tree content.</p>
  </blockquote>
  
  <p>This doesn't seem to place restrictions on which elements can have a <code>:after</code> (or <code>:before</code>) property. However, it seems to only work with <a href="http://jsfiddle.net/tAMks/">specific elements</a>... <code>&lt;p&gt;</code> works, <code>&lt;img&gt;</code> doesn't, <code>&lt;input&gt;</code> doesn't, <code>&lt;table&gt;</code> does. I'm could test more, but the point is made. Note that this seems pretty consistent across browsers. <strong>What determines whether an object can accept a <code>:before</code> and <code>:after</code> property?</strong></p>