function CheckUser(){
var username = $("#username").val();
var password = $("#password").val();
$.ajax({
type: "post",
url: "CheckUser",
dataType: "json",
data: {"username":username,"password":password},
success: function(data){
alert(data);
$("#head").html($.ajax({url: "head.jsp",async: false}).responseText)
}
经过调试，发现无法进入sucess回调函数，但是却能得到后台servlet处理的数据，求解答！！
