title: setting div as a background
body: <p><br>
  I have a div like which has an background, i like to set this div as an transparent background to certain dialog, like a jquery dialog. But the issue here is when the user scrolls the transparent div is also moving. i want this transparent div to be fixed even the scroll bar   moves. How can i achieve this? Thanks.  </p>
  
  <p><strong>Sample Code:</strong>  </p>
  
  <p>doc is an instance of html document. [doc  instanceof HTMLDocument] </p>
  
  <pre><code>&lt;div id=hiox1002  align=center style='display: none; z-index:3;opacity:0.4;\
              filter:alpha(opacity=40);background-image:url(http://funflys.com/images/bg.png);background-repeat:repeat;\
              width: "+doc.defaultView.innerWidth+"px; height: "+doc.defaultView.innerHeight+"px;/&gt;&lt;/div&gt;
  </code></pre>
  
  <p>I am trying this for an firefox add on</p>