cookie删除的怪异问题

最近在解决一个多语言的问题。用到了cookie. 于是就想彻底了解一下cookie.没想到遇到了一个非常奇怪的问题，一直不得其解，就写这篇文章来这询问各位了。

环境：

vs2008和IE6

页面代码如下

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default"
    UICulture="auto" Culture="auto" meta:resourcekey="PageResource1" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    </div>
    <asp:Label ID="lblUserName" runat="server" meta:resourcekey="lblUserName" Text="Label"></asp:Label>
    <%--<asp:Label ID="lblUserName" runat="server" Text="<%$ Resources:Default.aspx.zh-CN.resx,lblUserName%>"></asp:Label>--%>
    <asp:Image ImageUrl="~/Images/213hws7.gif" ID="imgNew" runat="server" meta:resourcekey="imgNew" />
    <asp:DropDownList ID="ddlMultiLanguage" runat="server" AutoPostBack="true" OnSelectedIndexChanged="ddlMultiLanguage_SelectedIndexChanged">
        <asp:ListItem Value="en-us" Text="Englist" Selected="True"></asp:ListItem>
        <asp:ListItem Value="zh-cn" Text="简体中文"></asp:ListItem>
    </asp:DropDownList>
    <asp:Button ID="Button1" runat="server" onclick="Button1_Click" Text="Button" />
    </form>
</body>
</html>

后台代码如下：

using System;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;

public partial class _Default : BasePage
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            if (Request.Cookies["language_cookie"] != null && Request.Cookies["language_cookie"].Value != string.Empty)
            {
                string language_cookie = Request.Cookies["language_cookie"].Value.ToLower();
                this.ddlMultiLanguage.SelectedValue = Request.Cookies["language_cookie"].Value.ToLower();
            }
            else
            {
                this.ddlMultiLanguage.SelectedValue = Request.Headers["accept-language"].Split(",".ToCharArray())[0].ToString().ToLower();
            }
        }

    }

    protected void ddlMultiLanguage_SelectedIndexChanged(object sender, EventArgs e)
    {
        if (Request.Cookies["language_cookie"] != null && Request.Cookies["language_cookie"].Value != string.Empty)
        {
            Request.Cookies["language_cookie"].Value = this.ddlMultiLanguage.SelectedValue;
            Request.Cookies["language_cookie"].Expires = DateTime.Now.AddDays(10);
        }
        else
        {
            Response.Cookies["language_cookie"].Value = this.ddlMultiLanguage.SelectedValue;
            Response.Cookies["language_cookie"].Expires = DateTime.Now.AddDays(10);
        }

            String selectedLanguage = this.ddlMultiLanguage.SelectedValue;
            UICulture = selectedLanguage;
            Culture = selectedLanguage;

            System.Threading.Thread.CurrentThread.CurrentCulture = System.Globalization.CultureInfo.CreateSpecificCulture(selectedLanguage);
            System.Threading.Thread.CurrentThread.CurrentUICulture = new System.Globalization.CultureInfo(selectedLanguage);

    }

    protected void Button1_Click(object sender, EventArgs e)
    {
        //Request.Cookies.Clear();
        //Response.Cookies.Clear();
        //Response.Cookies.Remove("language_cookie");
        //Response.Cookies["language_cookie"].Expires = DateTime.Now.AddYears(-1000);
        Response.Cookies["language_cookie"].Expires = DateTime.Now.AddDays(-100);

    }

    protected override void InitializeCulture()
    {
        base.InitializeCulture();
    }

}

问题：

我在Button1_Click事件中，设置了cookie的过期时间，这样浏览器就可以删除cookie. 我查看了一下下面两个文件夹

C:\Documents and Settings\user\Cookies

C:\Documents and Settings\user\Local Settings\Temporary Internet Files

里边的cookie确实不存在了。

但是，当我再次启动程序，发现在 Page_Load事件中的Request.Cookies["language_cookie"]竟然还存在的。我个人觉得在点击button触发Button1_Click事件后，cookie应该是不删除了，再次启动程序的时候Request.Cookies["language_cookie"]应该是不存在的。所以很疑惑。请各位指教。

多谢多谢！

补充：当我设置一个很大的值Response.Cookies["language_cookie"].Expires = DateTime.Now.AddYears(-1000); 效果就与推断的一样。Request.Cookies["language_cookie"]就真的不存在了。

--------------------编程问答--------------------
按理说这样已经可以了。
Response.Cookies["language_cookie"].Expires = DateTime.Now.AddDays(-100);
--------------------编程问答-------------------- 看不明白    --------------------编程问答-------------------- ding --------------------编程问答-------------------- protected void Button1_Click(object sender, EventArgs e)
    {

  if (Request.Cookies["language_cookie"] != null)
   {
    HttpCookie myCookie = new HttpCookie("language_cookie");
    myCookie.Expires = DateTime.Now.AddDays(-1d);
    Response.Cookies.Add(myCookie);
   }
    } --------------------编程问答-------------------- 为什么数字要设置为负的

--------------------编程问答-------------------- tulong403看不明白？首先感谢你的回复请问什么地方不明白，你可以把代码复制下来，在自己本地尝试一下。 --------------------编程问答-------------------- 设置cookie 的管理相关。在 config里设置吧。 --------------------编程问答-------------------- 能说的具体一些吗？如何在config里设置？

补充：.NET技术 ,  ASP.NET