function AbrirAjax() {
    var xmlhttp;
    try {
     //Para o Internet Explorer
     xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
    }
    catch(e) {
     try {
      //IE8
      xmlhttp = getXMLHTTP();
     }
     catch(ex) {
      try {
       //Para todos os outros Browsers (FireFox,Opera, etc ...)
       xmlhttp = new XMLHttpRequest();
      }
      catch(exc) {
       alert("Seu navegador não tem recursos para uso de Ajax");
       xmlhttp = null;
      }
     }
    }
    return xmlhttp;
    }


  /*  function AbrirAjax() 
    { 
    var xmlhttp; 
    try 
      { 
      // Firefox, Opera 8.0+, Safari 
      xmlhttp=new XMLHttpRequest(); 
      } 
    catch (e) 
      { 
      // Internet Explorer 
      try 
        { 
        xmlhttp=new ActiveXObject("Msxml2.XMLHTTP"); 
        } 
      catch (e) 
        { 
        xmlhttp=new ActiveXObject("Microsoft.XMLHTTP"); 
        } 
      } 
    return xmlhttp; 
    }   */

/*function AbrirAjax() 
    { 
var xmlhttp;
if (window.XMLHttpRequest)
  {// code for IE7+, Firefox, Chrome, Opera, Safari
  xmlhttp=new XMLHttpRequest();
  }
else
  {// code for IE6, IE5
  xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
  }
}
*/