Redirect to page not found page if the url does't exist in mVC

I need to redirect the user to page not found page if the url doent exist. if the user copy the url and paste it on the rbowser, the page shows page not found method.

in this i need to redirect the user to page not found page

What is the difference between redirect () and RedirectToAction () in MVC?

RedirectToAction is meant for doing 302 redirects within your application and gives you an easier way to work with your route table. Redirect is meant for doing 302 redirects to everything else, specifically external URLs, but you can still redirect within your application, you just have to construct the URLs yourself.

See this:

How can I properly handle 404 in ASP.NET MVC?

which refers to this:

http://blogs.microsoft.co.il/blogs/shay/archive/2009/03/06/real-world-error-hadnling-in-asp-net-mvc-rc2.aspx