You can use Ajax timer control with ASP.net,
eg for 40sec
<html dir="ltr" xmlns="<a rel="nofollow" target="_new"
href="http://www.w3.org/1999/xhtml">">www.w3.org/.../xhtml"></a>
<script runat="server">
Protected Sub Timer1_Tick(ByVal sender As Object, ByVal e As System.EventArgs)
Response.Redirect("~/Default.aspx")
End Sub
</script>
<body>
<form id="form1" runat="server">
<h1>Submission successful!</h1>
Thank you for your submission
If
you are not redirected in 40 seconds, click <asp:HyperLink
runat="server" ID="lnkredirect" NavigateUrl="~/Default.aspx"
Text="here"></asp:HyperLink>
<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
<asp:Timer ID="Timer1" runat="server" EnableViewState="false" Interval="5000" OnTick="Timer1_Tick">
</asp:Timer>
</form>
</body>
</html>
you can read more from here
http://www.asp.net/AJAX/Documentation/Live/tutorials/TimerControlWithUpdatePanelsTutorial.aspx