Add Global.asax page:
add the following code in that file.
in the Application_End method clear all your session data
<![CDATA[<%@ Application Language="C#" %>]]>
<script runat="server">
void Application_Start(object sender, EventArgs e)
{
}
void Application_End(object sender, EventArgs e)
{
}
void Application_Error(object sender, EventArgs e)
{
}
void Session_Start(object sender, EventArgs e)
{
}
void Session_End(object sender, EventArgs e)
{
}
</script>
i hopes it hepls u.