Custom Errors Work Locally Not Once Deployed On IIS

I have the following:

Web.config

<system.web> <authentication mode="None" /> <compilation debug="true" targetFramework="4.5" /> <httpRuntime targetFramework="4.5" /> <customErrors mode="On" defaultRedirect="~/Error/ShowError"> <error redirect="~/Error/ShowError/400" statusCode="400" /> <error redirect="~/Error/ShowError/401" statusCode="401" /> <error redirect="~/Error/ShowError/403" statusCode="403" /> <error redirect="~/Error/ShowError/404" statusCode="404" /> </customErrors> </system.web> 

ErrorController

[AllowAnonymous] public class ErrorController : Controller { public ViewResult ShowError(int id) { Response.StatusCode = id; switch (id) { case 400: return View("~/Views/Error/400.cshtml"); case 401: return View("~/Views/Error/401.cshtml"); case 403: return View("~/Views/Error/403.cshtml"); case 404: return View("~/Views/Error/404.cshtml"); default: return View("~/Views/Error/404.cshtml"); } } } 

FilterConfig

 public static void RegisterGlobalFilters(GlobalFilterCollection filters) { //filters.Add(new HandleErrorAttribute()); } 

Locally everything works fine, I get a custom error page and am happy, however as soon as I deploy the site to my web server, I no longer get my custom error messages and only the generic:

Do I need to add anything specific for the IIS configuration in my online environment?

I've compared the local Web.config with the deployed Web.config and there isn't anything different (that I can see).