SOURCE

var request;
try{
  request = new XMLHttpRequest();//Ie7
}cache(e){
  request = new ActiveXObject('Microsoft.XMLHTTP');ie6以下
}

request.open('post','http.com',true);
request.send();

request.onreadystatechange = function() {
  if(request.readystate == 4){
    if (request.status == '200'){
      document.getElementById('myDiv').innerHTML = request.responseText;
    }else{
      alert("出错了"request.status);
    }
  }
}