title: Getting an error Value cannot be null or empty. Parameter name: URL
body: <p>Here is my code. Please some one help me desperately needed the code above mentioned.</p>
  
  <pre><code>    [HttpGet]
      public ActionResult Index(string returnUrl)
      {
          ViewBag.ReturnUrl = returnUrl;
          return View();
      }
  
      [HttpPost]
      public ActionResult Index(LoginModel loginModel, string returnUrl)
      {
          if (ModelState.IsValid)
          {
              if (loginModel.Username == "user" &amp;&amp; loginModel.Password == "password")
              {
                  FormsAuthentication.SetAuthCookie(loginModel.Username, true);
                  return Redirect(returnUrl);
              }
              else
              {
                  ModelState.AddModelError("", "The username or password provided is incorrect.");
              }
          }
  
          ViewBag.ReturnUrl = returnUrl;
  
          return View(loginModel);
      }
  </code></pre>
  
  <p>And I am following this link:
  <a href="http://www.primaryobjects.com/CMS/Article155.aspx" rel="nofollow">http://www.primaryobjects.com/CMS/Article155.aspx</a></p>