/*
url:xml的路径
id:要显示的div的id
*/
function ajaxLoader(url,id) {
  if (document.getElementById) {
    var x = (window.ActiveXObject) ? new ActiveXObject("Microsoft.XMLHTTP") : new XMLHttpRequest();
  }
  if (x) {
    x.onreadystatechange = function() {
      if (x.readyState == 4 && x.status == 200) {
        el = document.getElementById(id);
        el.innerHTML = x.responseText;
      }
    }
    x.open("GET",url,true);
    x.send(null);
  }
}

页面调用

ajaxLoader('demo.xml','contentDIV')