前台：<div >123123</div>

后台OnLoad方法：

  if (Session["__LoginUser"] != null)
            {
                if (Session["__LoginUser"] is User)
                {
                    this.FindControl("divZyszfx").Visible = false;
                }
                else if (Session["__LoginUser"] is Master)
                {

                    this.FindControl("divZyszfx").Visible = true;
                }
            }