function objetoAjax(){
	var xmlhttp=false;
	try{
		xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
	}catch (e){
		try{
			xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
		}catch (E){
			xmlhttp = false;
		}
	}
	if (!xmlhttp && typeof XMLHttpRequest!='undefined'){
		xmlhttp = new XMLHttpRequest();
	}
	return xmlhttp;
}
function div_refresh(pagina){
	var pg_php = pagina;
	var divCambio  = document.getElementById('dinamo');
	ajax = objetoAjax();
	ajax.open("GET", pg_php);
	ajax.onreadystatechange = function(){
		if (ajax.readyState==4){
			divCambio.innerHTML = ajax.responseText;
		}
	}
	ajax.send(null);
}