<%@ Page Language="C#" %>
<script runat="server">
  protected void Page_Load(object sender, EventArgs e)
  {
    HttpCookie h = new HttpCookie("url", Request.RawUrl);
    Response.Cookies.Add(h);
  }
</script>
<frameset cols="90,*">
<frame src="1.aspx"/>
<frame src="2.aspx"/>
</frameset>