CSS positioning div above another div when not in that order in the HTML

$('#secondDiv').insertBefore('#firstDiv');

$('.swapMe').each(function(i, el) {
    $(el).insertBefore($(el).prev());
});

#wrapper { position: relative; }
#firstDiv { position: absolute; height: 100px; top: 110px; }
#secondDiv { position: absolute; height: 100px; top: 0; }

<style>
#firstDiv {
    position:absolute; top:100%;
}
#wrapper {
    position:relative;
}

position : absolute;

fd = document.getElementById( 'firstDiv' );
sd = document.getElementById( 'secondDiv' );
fd.parentNode.removeChild( fd );
sd.parentNode.insertAfter( fd, sd );

<div class="product">
<h2>Greatest Product Ever</h2>
<p class="desc">This paragraph appears in the source code directly after the heading and will appear in the search results.</p>
<p class="sidenote">Note: This information appears in HTML after the product description appearing below.</p>
</div>

.product { width: 400px; }
.desc { margin-top: 5em; }
.sidenote { margin-top: -7em; }

#firstDiv {
    float: left;
}

#secondDiv {
    float: left;
    clear: left;
}

#wrapper { position: relative; margin-top: 4em; }
#firstDiv { position: absolute; top: 0; width: 100%; }
#secondDiv { position: absolute; bottom: 0; width: 100%; }

#firstDiv { position: relative; top: YYYpx; height: XXXpx; }
#secondDiv { position: relative; top: -XXXpx; height: YYYpx; }

<?xml version="1.0" encoding="iso-8859-1"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<meta http-equiv="Content-Language" content="en" />
<meta name="language" content="en" />
<title>Vertical Centering in CSS2 - Example (IE, FF & Chrome tested) - This is so tricky!!!</title>
<style type="text/css">
 html,body{
  margin:0px;
  padding:0px;
  width:100%;
  height:100%;
 }
 div.BloqueTipoTabla{
  display:table;margin:0px;border:0px;padding:0px;width:100%;height:100%;
 }
 div.BloqueTipoFila_AltoAjustadoAlContenido{
  display:table-row;margin:0px;border:0px;padding:0px;width:100%;height:auto;
 }
 div.BloqueTipoFila_AltoRestante{
  display:table-row;margin:0px;border:0px;padding:0px;width:100%;height:100%;
 }
 div.BloqueTipoCelda_AjustadoAlContenido{
  display:table-cell;margin:0px;border:0px;padding:0px;width:auto;height:auto;
 }
 div.BloqueTipoCelda_RestanteAncho{
  display:table-cell;margin:0px;border:0px;padding:0px;width:100%;height:auto;
 }
 div.BloqueTipoCelda_RestanteAlto{
  display:table-cell;margin:0px;border:0px;padding:0px;width:auto;height:100%;
 }
 div.BloqueTipoCelda_RestanteAnchoAlto{
  display:table-cell;margin:0px;border:0px;padding:0px;width:100%;height:100%;
 }
 div.BloqueTipoContenedor{
  display:block;margin:0px;border:0px;padding:0px;width:100%;height:100%;position:relative;
 }
 div.BloqueTipoContenedor_VerticalmenteCentrado{
  display:block;margin:0px;border:0px;padding:0px;width:100%;height:auto;position:relative;top:50%;
 }
 div.BloqueTipoContenido_VerticalmenteCentrado_Oculto{
  display:block;margin:0px;border:0px;padding:0px;width:100%;height:auto;visibility:hidden;position:relative;top:50%;
 }
 div.BloqueTipoContenido_VerticalmenteCentrado_Visible{
  display:block;margin:0px;border:0px;padding:0px;width:100%;height:auto;visibility:visible;position:absolute;top:-50%;
 }
</style>
</head>
<body>
<h1>Vertical Centering in CSS2 - Example<br />(IE, FF & Chrome tested)<br />This is so tricky!!!</h1>
<div class="BloqueTipoTabla" style="margin:0px 0px 0px 25px;width:75%;height:66%;border:1px solid blue;">
 <div class="BloqueTipoFila_AltoAjustadoAlContenido">
  <div class="BloqueTipoCelda_AjustadoAlContenido">
   [1,1]
  </div>
  <div class="BloqueTipoCelda_AjustadoAlContenido">
   [1,2]
  </div>
  <div class="BloqueTipoCelda_RestanteAncho">
   [1,3]
  </div>
  <div class="BloqueTipoCelda_AjustadoAlContenido">
   [1,4]
  </div>
 </div>
 <div class="BloqueTipoFila_AltoAjustadoAlContenido">
  <div class="BloqueTipoCelda_AjustadoAlContenido">
   [2,1]
  </div>
  <div class="BloqueTipoCelda_AjustadoAlContenido">
   [2,2]
  </div>
  <div class="BloqueTipoCelda_RestanteAncho">
   [2,3]
  </div>
  <div class="BloqueTipoCelda_AjustadoAlContenido">
   [2,4]
  </div>
</div>
 <div class="BloqueTipoFila_AltoRestante">
  <div class="BloqueTipoCelda_RestanteAlto">
   <div class="BloqueTipoContenedor" style="border:1px solid lime;">
    <div class="BloqueTipoContenedor_VerticalmenteCentrado" style="border:1px dotted red;">
     <div class="BloqueTipoContenido_VerticalmenteCentrado_Oculto">
     The cell [3,1]
     <br />
     *&nbsp;*&nbsp;*&nbsp;*
     <br />
     *&nbsp;*&nbsp;*&nbsp;*
     <br />
     *&nbsp;*&nbsp;*&nbsp;*
     <br />
     Now&nbsp;is&nbsp;the&nbsp;highest&nbsp;one
     </div>
     <div class="BloqueTipoContenido_VerticalmenteCentrado_Visible" style="border:1px dotted blue;">
     The cell [3,1]
     <br />
     *&nbsp;*&nbsp;*&nbsp;*
     <br />
     *&nbsp;*&nbsp;*&nbsp;*
     <br />
     *&nbsp;*&nbsp;*&nbsp;*
     <br />
     Now&nbsp;is&nbsp;the&nbsp;highest&nbsp;one
     </div>
    </div>
   </div>
  </div>
  <div class="BloqueTipoCelda_RestanteAlto">
   <div class="BloqueTipoContenedor" style="border:1px solid lime;">
    <div class="BloqueTipoContenedor_VerticalmenteCentrado" style="border:1px dotted red;">
     <div class="BloqueTipoContenido_VerticalmenteCentrado_Oculto">
      This&nbsp;is<br />cell&nbsp;[3,2]
     </div>
     <div class="BloqueTipoContenido_VerticalmenteCentrado_Visible" style="border:1px dotted blue;">
      This&nbsp;is<br />cell&nbsp;[3,2]
     </div>
    </div>
   </div>
  </div>
  <div class="BloqueTipoCelda_RestanteAnchoAlto">
   <div class="BloqueTipoContenedor" style="border:1px solid lime;">
    <div class="BloqueTipoContenedor_VerticalmenteCentrado" style="border:1px dotted red;">
     <div class="BloqueTipoContenido_VerticalmenteCentrado_Oculto">
      This is cell [3,3]
      <br/>
      It is duplicated on source to make the trick to know its variable height
      <br />
      First copy is hidden and second copy is visible
      <br/>
      Other cells of this row are not correctly aligned only on IE!!!
     </div>
     <div class="BloqueTipoContenido_VerticalmenteCentrado_Visible" style="border:1px dotted blue;">
      This is cell [3,3]
      <br/>
      It is duplicated on source to make the trick to know its variable height
      <br />
      First copy is hidden and second copy is visible
      <br/>
      Other cells of this row are not correctly aligned only on IE!!!
     </div>
    </div>
   </div>
  </div>
  <div class="BloqueTipoCelda_RestanteAlto">
   <div class="BloqueTipoContenedor" style="border:1px solid lime;">
    <div class="BloqueTipoContenedor_VerticalmenteCentrado" style="border:1px dotted red;">
     <div class="BloqueTipoContenido_VerticalmenteCentrado_Oculto">
      This&nbsp;other is<br />the cell&nbsp;[3,4]
     </div>
     <div class="BloqueTipoContenido_VerticalmenteCentrado_Visible" style="border:1px dotted blue;">
      This&nbsp;other is<br />the cell&nbsp;[3,4]
     </div>
    </div>
   </div>
  </div>
 </div>
 <div class="BloqueTipoFila_AltoAjustadoAlContenido">
  <div class="BloqueTipoCelda_AjustadoAlContenido">
   [4,1]
  </div>
  <div class="BloqueTipoCelda_AjustadoAlContenido">
   [4,2]
  </div>
  <div class="BloqueTipoCelda_RestanteAncho">
   [4,3]
  </div>
  <div class="BloqueTipoCelda_AjustadoAlContenido">
   [4,4]
  </div>
 </div>
</div>
</body>
</html>