How can I redirect to "page not found" with MVC3?

I have some links in Google that I now no longer expect to work. All of the links look like this:

www.abc.com/xx/que=xxxxxxxxxxx

Where x can be anything.

Can someone tell me how I can set up a route and controller action that will return a 404 to google? I guess I need to set it up with a mask that includes "que" but I am not so sure how to do this.

Add a new route to the top of your global.asax. This will catch requests of the form xx/que={anything} using a regular expression to define the "que" argument.

routes.MapRoute(
    "PageNotFound", 
    "xx/{que}",
    new { controller = "Error", action = "NotFound" },
    new { que = "que=.*" });

This would also assume you have an ErrorController with action NotFound and corresponding view named NotFound.aspx in your /Views/Error/ directory.

public class ErrorController : Controller
{
    public ActionResult NotFound()
    {
        Response.StatusCode = 404;
        return View();
    }
}