first you need to check your webconfig file

and set like   <globalization  culture="en-US"  uiCulture="en-US" requestEncoding="utf-8" responseEncoding="utf-8"/>

write code in global .asax file

 protected void Application_AcquireRequestState(object sender, EventArgs e)
    {

        string culture = System.Globalization.CultureInfo.CurrentCulture.Name;
        if (HttpContext.Current.Session != null && HttpContext.Current.Session["Culture"] != null)
        {
            culture = Convert.ToString(HttpContext.Current.Session["Culture"]);
        }
        System.Globalization.CultureInfo cultureInfo = new System.Globalization.CultureInfo(culture);
        System.Threading.Thread.CurrentThread.CurrentCulture = cultureInfo;
        System.Threading.Thread.CurrentThread.CurrentUICulture = cultureInfo;
    }

and add resource file for particular page

and call resource pages string in aspx page control

  <asp:Literal ID="ltrJunePromotionalCodeHeading" Text="" runat="server" meta:resourcekey="ltrJunePromotionalCodeHeading"></asp:Literal>

it will help you to convert data into multilingual....

http://weblogs.asp.net/sreejukg/archive/2010/11/23/multi-lingual-web-applications-using-asp-net-4.aspx