var XMLHttpRequestObject = false;

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

function pedirDatos(fuenteDatos, divID){
        if(XMLHttpRequestObject) {
               var obj = document.getElementById(divID);
               XMLHttpRequestObject.open("GET", fuenteDatos);
               XMLHttpRequestObject.onreadystatechange = function(){
                       if (XMLHttpRequestObject.readyState == 4 && XMLHttpRequestObject.status == 200) {
                           obj.innerHTML = XMLHttpRequestObject.responseText;
                       }
               }
               XMLHttpRequestObject.send(null);
        } 
}