var xmlhttp = getXmlHttpRequest();
  
function getXmlHttpRequest()
{
   if (window.XMLHttpRequest)
   {
      return new XMLHttpRequest();
   }
   else if (window.ActiveXObject)
   {
      try
      {
         return new ActiveXObject("Msxml2.XMLHTTP");
      }
      catch (e)
      {
         try
         {
            return new ActiveXObject("Microsoft.XMLHTTP");
         }
         catch (e){}
      }
   }
}

function requisicao(_strNomePagina)
{
      xmlhttp.open("GET", _strNomePagina, true);
      xmlhttp.setRequestHeader("Content-Type", "text/html; charset=iso-8859-1");
      xmlhttp.setRequestHeader("Cache-Control", "no-store, no-cache, must-revalidate");
      xmlhttp.setRequestHeader("Cache-Control", "post-check=0, pre-check=0");
      xmlhttp.setRequestHeader("Pragma", "no-cache");
      xmlhttp.onreadystatechange = function()
      {
         if (xmlhttp.readyState==4)
         {
            document.getElementById('div_conteudo').innerHTML = xmlhttp.responseText;
         }
      }  
      xmlhttp.send(null);
}