Problem in pafe navigation using hyperlink

Hi,

i have a 2 hyperlink on a page. the 1st hyperlink refers to previous page and the 2nd hyperlink refer tp current page itself
it works fine, when click on 1st hyperlink it redirect to previous page. but it fails when i click on the 2nd hyperlink then again on 1st hyperlink it would not get redirected.
below is my code:
if (Session["ssn1stPage"] != null)
{
string url = Request.Url.AbsoluteUri;
string urlPrevPage = Page.Request.UrlReferrer.AbsoluteUri;
Session["ssn2ndPage"] = "2ndPage".ToString();

hypLnk1.Text = Session["ssn1stPage"].ToString();
hypLnk2.Text = Session["ssn2ndPage"].ToString();

hypLnk1.NavigateUrl = urlPrevPage;
hypLnk2.NavigateUrl = url;
}
else
{
Response.Redirect("1stPage.aspx",true);
}
problem is tht when i click on the 2nd hyperlnk, the value of string urlPrevPage changes to the current one.
Please suggest ...