asp.net网站问题请教

我用下面的方式弹出对话框
RegisterStartupScript("js", " <script>alert('对不起您没有该权限') </script>");

然后我再刷新页面，页面会提示：“不重新发送信息，则无法刷新网页，请单击重试”

---

C# code:
/// <summary>
/// 显示消息提示对话框
/// </summary>
/// <param name="page">当前页面指针，一般为this</param>
/// <param name="msg">提示信息</param>
public static void Show(System.Web.UI.Page page, string msg)
{
page.RegisterStartupScript("message", "<script language='javascript' defer>alert('" + msg.ToString() + "');</script>");
}

---

    /// <summary>
    /// 显示消息提示对话框
    /// </summary>
    /// <param name="page">当前页面指针，一般为this </param>
    /// <param name="msg">提示信息 </param>
    public static void Show(System.Web.UI.Page page, string msg)
    {
        page.RegisterStartupScript("message", " <script language='javascript' defer>alert('" + msg.ToString() + "'); </script>");
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