HTTP 404 : Resource Not found - Custom error

I am a newbie to MVC.

I am trying to create a custom error page to show when the user is looking for an unavailable resource. I followed a few articles and was able to show a custom error page. ASP.NET MVC 404 Error Handling.

I have created an error Controller with 'NotFound404()' action method and view is created with the same name 'NotFound404.cshtml'.

public class ErrorController : Controller { // GET: Error public ActionResult NotFound404() { return View(); } } 

Web.config

<system.web> <customErrors mode="On"> <error statusCode="404" redirect="~/Error/NotFound404"/> </customErrors> </system.web> 

When I try to access any unknown resource, I can see the notfound404. But when I inspect URL it shows as 'http://localhost:xyzw/Error/NotFound404?aspxerrorpath=/New'.

Why do i get such weird URL? and I am not using any aspx pages but it shows aspx in the URL. HTTP status under F12-Developer tools- Network - shows 200 which isn't correct. How do I rectify this?

And when I tried to access any static HTML page instead of a new controller/ action-view

<system.web> <customErrors mode="On"> <error statusCode="404" redirect="~/Shared/NotFound.html"/> </customErrors> </system.web> 

404 Error occurs -- is this error because it is looking up for wrong path?

How do I fix these errors?
Please show a right way to configure these error handling strategies.

Thanks in advance.