I started playing around with the ASP.NET MVC 5 preview and everything has been going fine so far (I can only recommend it).
However, I wonder where I can set the Login-Url for the Built-In [Authorize]-Attribute. I've moved the AccountController to a an area, so the path to the Login action is no longer /Account/Login but MyArea/Account/Login, which is ignored by the [Authorize]-Attribute, which in turn means, that whenever one navigates to a controller or action with the attribute set, one is redirected to the wrong path /Account/Login.
Look in web.config for a section like this:
<authentication mode="Forms">
<forms loginUrl="~/Account/LogOn" timeout="2880" />
</authentication>
Change the loginUrl value to point to your updated login page.