How to use the AJAX for login in web applications ?

<asp:Panel ID="loginPanel" runat="server" Style="display: none">     <asp:Login ID="LoginCtrl" runat="server"          CssSelectorClass="THBLogin"         FailureText="Identifiant incorrect ! Essayez ? nouveau..."         LoginButtonText="S'identifier"                   PasswordLabelText="Mot de Passe"          PasswordRequiredErrorMessage="Le mot de passe est requis."         RememberMeText="Se souvenir de moi la prochaine fois."          TitleText="S'identifier"         UserNameLabelText="Email"          UserNameRequiredErrorMessage="L'email est requis."          CreateUserText="S'enregistrer"          CreateUserUrl="/Register.aspx"          PasswordRecoveryText="Mot de passe oubli? ?"          PasswordRecoveryUrl="/PasswordRecovery.aspx" /> asp:Panel>

Then you had the PopupControlExtender:

<ajaxToolkit:PopupControlExtender ID="PopEx" runat="server"
    TargetControlID="loginHyperLink"
    PopupControlID="loginPanel"            
    Position="Left" />

http://weblogs.asp.net/lkempe/archive/2007/01/28/login-control-in-an-asp-net-ajax-toolkit-popupcontrolextender-with-a-close-button.aspx

http://weblogs.asp.net/andrewfrederick/archive/2008/02/18/a-client-side-ajax-login-for-asp-net.aspx

Hope this helps you.