I got a error in my MVC4 application regarding webSecurity.

 public ActionResult Login(user model, string returnUrl="/Home")
 {
    if (ModelState.IsValid && WebSecurity.Login(model.UserFirstName, model.Password))
           {
               return RedirectToLocal(returnUrl);
           }

           // If we got this far, something failed, redisplay form
  ModelState.AddModelError("", "The user name or password provided is incorrect.");
  return View(model);
}

You must call the "WebSecurity.InitializeDatabaseConnection" method before you call any other method of the "WebSecurity" class. This call should be placed in an _AppStart.cshtml file in the root of your site.