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 ajaxpage(pagina,boton){
	cont = document.getElementById('contenido');
	
	ajax=objetoAjax();
	
    ajax.open("GET", pagina);
    ajax.onreadystatechange = function(){
		if (ajax.readyState == 4 && ajax.status == 200) {
			cont.innerHTML = ajax.responseText;
		}
	}
	ajax.send(null);
}