title: div is null in ie but in mozila and opera
body: <pre><code>&lt;div id="a"&gt;&lt;/div&gt;
  
  if($("#a").is(':empty') )
        alert("empty");
  </code></pre>
  
  <p>In IE8, it shows <code>alert</code> but Mozila 3.6 and Opera 11 do not show the <code>alert</code>. Why?</p>
  
  <p><strong>Answer:</strong></p>
  
  <pre><code>if(!$.trim( $("#a").html() ) )
     alert("empty");
  </code></pre>
  
  <p>this code run in ie and mozila</p>