function ajax(url)
{

req = null;

if (window.XMLHttpRequest) {
req = new XMLHttpRequest();
req.onreadystatechange = processReqChange;
req.open("GET",url,true);
req.send(null);

} else if (window.ActiveXObject) {
req = new ActiveXObject("Microsoft.XMLHTTP");
if (req) {

req.onreadystatechange = processReqChange;
req.open("GET",url,true);

req.send();
}
}
}

function processReqChange()
{
if (req.readyState == 1) {
document.getElementById('pagina').innerHTML = 'Carregando, por favor aguarde...';
}


else if (req.readyState == 4) {


if (req.status ==200) {
document.getElementById('pagina').innerHTML = req.responseText;
} else {
alert("Houve um problema ao obter os dados:n" + req.statusText);
}
}
}