function goAjax(url, metodo, modo, tagRetorno, parametros) 
{

 if (window.XMLHttpRequest)
{// code for IE7+, Firefox, Chrome, Opera, Safari
    xmlhttp=new XMLHttpRequest();
}
else
{// code for IE6, IE5
    try
    {
        xmlhttp = new ActiveXObject("Msxml2.XMLHTTP") // Versão 6
    }
    catch(e)
    {
        try
        {
            xmlhttp = new ActiveXObject("Microsoft.XMLHTTP")  // Versão 5.5
        }
        catch(e)
        {
        }
    }
}

    if(metodo == "GET") 
    {
       xmlhttp.open("GET", url, modo);
    } 
    else 
    {        
        xmlhttp.open("POST", url, modo);
        xmlhttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded; 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) 
        {
            retorno = xmlhttp.responseText;
            document.getElementById(tagRetorno).innerHTML = retorno;
        }
    }
      
        xmlhttp.send(parametros);

}