message box with OK in C# using asp.net

message box with OK in C# using asp.net :

aspx:cs :

  protected void btn_tomail_Click(object sender, EventArgs e)

        {

     ClientScript.RegisterStartupScript(Page.GetType(), "alert", 

                             "alert('Password Sent Your EmailID !!');

                              window.location='Login1.aspx';", true);

      }