Google has known only one of my website languages?

Hi.
I create a multiple language website and i use a Link button for change language. In Link button I use this code:
aspx page : 
<asp:LinkButton ID="Language" runat="server" CommandArgument="<%$Resources:Resource, LanguageCode %>" onclick="Language_Click"><%=Resources.Resource.Language %></asp:LinkButton>
aspx code page :
Session["culture"] = Language.CommandArgument; Response.Redirect(Request.Path);
I use App_GlobalResources for languages and I define my keywords on it. To switch between languages, i use BasePage class.
BasePage class Code:
protected override void InitializeCulture() { //retrieve culture information from session string culture = Convert.ToString(Session["culture"]);
//check whether a culture is stored in the session if (culture.Length > 0) Culture = culture;
...