sharepoint 2010 foundation signout issue

Hi Karunanithi,

Below code will clear out all the cookies. Although I have only used this code for Claims Based mode, try and see if it works for you as well:

protected override void OnLoad(EventArgs e)
        {
            base.OnLoad(e);

            ClientScriptManager cm = Page.ClientScript;

            String ulsScript = "function ULSLogout(){var o=new Object;o.ULSTeamName=\"Microsoft SharePoint Foundation\";o.ULSFileName=\"LogOut.aspx\";return o;}";
            cm.RegisterClientScriptBlock(this.GetType(), "UlSLogout", ulsScript, true);

            String closeBrowser = "function _spBodyOnLoad() {ULSLogout:; try { document.execCommand(\"ClearAuthenticationCache\"); } catch (e) { }       window.close(); }";
            cm.RegisterStartupScript(this.GetType(), "CloseBrowser", closeBrowser, true);

            ScriptManager.RegisterStartupScript(this, this.GetType(), "CloseBrowser", "_spBodyOnLoad();", true);
            RemoveCookiesAndRedirect();            
        } 

private void RemoveCookiesAndRedirect()
        {

            if (this.Context.Session != null)
            {
                this.Context.Session.Clear();
            }
            string str = string.Empty;

            if (this.Context.Request.Browser[SupportsEmptyStringInCookieValue] == "false")
            {
                str = "NoCookie";
            }

            HttpCookie cookie = this.Context.Request.Cookies[CookieWssKeepSessionAuthenticated];
            
            if (cookie != null)
            {
                cookie.Value = str;
                this.Context.Response.Cookies.Remove(CookieWssKeepSessionAuthenticated);
                this.Context.Response.Cookies.Add(cookie);
            }

            HttpCookie cookie2 = this.Context.Request.Cookies[CookieWssKeepAuthenticated];

            if (cookie2 != null)
            {
                cookie2.Value = str;
                cookie2.Expires = new DateTime(1970, 1, 1);
                this.Context.Response.Cookies.Remove(CookieWssKeepAuthenticated);
                this.Context.Response.Cookies.Add(cookie2);
            }

            SPIisSettings iisSettingsWithFallback = SPsite.WebApplication.GetIisSettingsWithFallback(SPsite.Zone);

            if (iisSettingsWithFallback.UseClaimsAuthentication)
            {
                FederatedAuthentication.SessionAuthenticationModule.SignOut();
                int num = 0;
                using (IEnumerator<SPAuthenticationProvider> enumerator = iisSettingsWithFallback.ClaimsAuthenticationProviders.GetEnumerator())
                {
                    while (enumerator.MoveNext())
                    {
                        SPAuthenticationProvider current = enumerator.Current;
                        num++;
                    }
                }

                if ((num != 1) || !iisSettingsWithFallback.UseWindowsIntegratedAuthentication)
                {
                    
                    SPUtility.Redirect(BaseWebpart.FBA_Next_Step, SPRedirectFlags.Default, this.Context);
                }
            }
            else if (AuthenticationMode.Forms == SPSecurity.AuthenticationMode)
            {
                FormsAuthentication.SignOut();
                SPUtility.Redirect(BaseWebpart.FBA_Next_Step, SPRedirectFlags.Default, this.Context);
            }
            else if (AuthenticationMode.Windows != SPSecurity.AuthenticationMode)
            {
                throw new SPException();
            }

            SPUtility.Redirect("/_layouts/signout.aspx", SPRedirectFlags.DoNotEncodeUrl, this.Context);
        }

Cheers,

Vincent