title: get tag content by javascript of tag that "outside the document"
body: <p>I have this HTML source :</p>
  
  <pre><code>&lt;div id='fbResponse' style='display:none'&gt;{"key1":"value1","key2":"value2"}&lt;/div&gt;
  
  &lt;!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"&gt;
  &lt;html xmlns="http://www.w3.org/1999/xhtml"&gt;
  &lt;head&gt;
  &lt;title&gt;&lt;/title&gt;
      &lt;script type="text/javascript"&gt;
       ....
      &lt;/script&gt;
  &lt;/head&gt;
  &lt;body onload="initFB()" style="text-align: center"&gt;
      ....
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>How do i get the content-text of the div tag with id "fbResponse",
  I tried already the function </p>
  
  <pre><code>document.getElementById('tag id'),
  </code></pre>
  
  <p>It doesn't work ,i think it is because that the tag :</p>
  
  <pre><code>&lt;div id='fbResponse' style='display:none'&gt;{"key1":"value1","key2":"value2"}&lt;/div&gt;
  </code></pre>
  
  <p>is out of the "document" .</p>
  
  <p><strong>EDIT:</strong>
  The browser which I need it to work on is mobile Safari (iOS)</p>