Hi 

When I submit Login button without any FBA user details I am getting the below screen and also when entered incorrect user details I am not getting any error message.

Server Error in '/' Application.

---

Value cannot be null.
Parameter name: password

[ArgumentNullException: Value cannot be null.
Parameter name: password]
   Microsoft.SharePoint.IdentityModel.SPClaimsUtility.AuthenticateFormsUser(Uri context, String userName, String password) +526
   GG.Login.Custom.Layouts.GG.Login.Custom.Login.<OnLoggingIn>b__12_0() +202
   Microsoft.SharePoint.Utilities.SecurityContext.RunAsProcess(CodeToRunElevated secureCode) +177
   Microsoft.SharePoint.SPSecurity.RunWithElevatedPrivileges(WaitCallback secureCode, Object param) +502
   Microsoft.SharePoint.SPSecurity.RunWithElevatedPrivileges(CodeToRunElevated secureCode) +83
   GG.Login.Custom.Layouts.GG.Login.Custom.Login.OnLoggingIn(Object sender, LoginCancelEventArgs e) +125
   System.Web.UI.WebControls.LoginCancelEventHandler.Invoke(Object sender, LoginCancelEventArgs e) +0
   System.Web.UI.WebControls.Login.OnLoggingIn(LoginCancelEventArgs e) +11794473
   System.Web.UI.WebControls.Login.AttemptLogin() +97
   System.Web.UI.WebControls.Login.OnBubbleEvent(Object source, EventArgs e) +107
   System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs args) +50
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1669

 below is my code for login.aspx

using System;
using Microsoft.SharePoint;
using Microsoft.SharePoint.WebControls;
using Microsoft.SharePoint.IdentityModel.Pages;
using System.Web;
using Microsoft.SharePoint.Utilities;
using Microsoft.SharePoint.Administration;
using System.Web.UI.WebControls;
using Microsoft.SharePoint.IdentityModel;

namespace GG.Login.Custom.Layouts.GG.Login.Custom
{
    public partial class Login : FormsSignInPage
    {
        Label lblError = new Label();   
        
        public object ScriptManager { get; private set; }
        protected string UserIP { get { return HttpContext.Current.Request.UserHostAddress; } }

        public object LblError { get; private set; }
        

        protected void Page_Load(object sender, EventArgs e)
        {

            if (!IsPostBack)
            {
                
            }
        }

        //protected void Login_Click(object sender, EventArgs e)
        protected void OnLoggingIn(object sender, LoginCancelEventArgs e)
        {
            
          

            try
            {
                if (!(signInControl.UserName.Length > 0 && signInControl.Password.Length > 0))
                {
                    lblError.Visible = true;
                    //lblError.Text = "STOP";
                    lblError.Text = "User Name or Password can not be empty!";
                    //lblError.BoldFont = true;

                    //FailureText.Text = "User Name or Password can not be empty!";
                }
                else
                {
                    bool status = Microsoft.SharePoint.IdentityModel.SPClaimsUtility.AuthenticateFormsUser(Context.Request.UrlReferrer, signInControl.UserName, signInControl.Password);

                    if (!status)// if forms auth failed
                    {
                        lblError.Visible = true;
                        lblError.Text = "Wrong Userid or Password";
                        //FailureText.Visible = true;
                        //FailureText.Text = "Wrong Userid or Password";
                    }
                    else //if success
                    {
                        if (Context.Request.QueryString.Keys.Count > 1)
                        {
                            Response.Redirect(Context.Request.QueryString["Source"].ToString());
                        }
                        else
                            Response.Redirect(Context.Request.QueryString["ReturnUrl"].ToString());
                        lblError.Visible = false;
                        // Response.Redirect(SPContext.Current.Web.Url); //Use site url
                    }

                }
            }
            catch (Exception ex)
            {
                ex.ToString();
            }

        }

         void setupProvider()
        {
            if (null != SPContext.Current && null != SPContext.Current.Site)
            {
                SPIisSettings iisSettings = SPContext.Current.Site.WebApplication.IisSettings[SPUrlZone.Default];
                if (null != iisSettings && iisSettings.UseWindowsClaimsAuthenticationProvider)
                {
                    SPAuthenticationProvider provider = iisSettings.WindowsClaimsAuthenticationProvider;
                    RedirectToLoginPage(provider);
                }
            }
        }

        //borrowed from Microsoft.SharePoint.IdentityModel.LogonSelector
        private void RedirectToLoginPage(SPAuthenticationProvider provider)
        {
            string components = HttpContext.Current.Request.Url.GetComponents(UriComponents.Query, UriFormat.SafeUnescaped);
            string url = provider.AuthenticationRedirectionUrl.ToString();
            if (provider is SPWindowsAuthenticationProvider)
            {
                components = EnsureUrlSkipsFormsAuthModuleRedirection(components, true);
            }
            SPUtility.Redirect(url, SPRedirectFlags.Default, this.Context, components);
        }
        //borrowed from Microsoft.SharePoint.Utilities.SPUtility
        private string EnsureUrlSkipsFormsAuthModuleRedirection(string url, bool urlIsQueryStringOnly)
        {
            if (!url.Contains("ReturnUrl="))
            {
                if (urlIsQueryStringOnly)
                {
                    url = url + (string.IsNullOrEmpty(url) ? "" : "&");
                }
                else
                {
                    url = url + ((url.IndexOf('?') == -1) ? "?" : "&");
                }
                url = url + "ReturnUrl=";
            }
            return url;
        }
    }

}