Yet another solution.
Add ErrorControllers or static page to with 404 error information.
Modify your web.config (in case of controller).
<system.web>
<customErrors mode="On" >
<error statusCode="404" redirect="~/Errors/Error404" />
</customErrors>
</system.web>
Or in case of static page
<system.web>
<customErrors mode="On" >
<error statusCode="404" redirect="~/Static404.html" />
</customErrors>
</system.web>
This will handle both missed routes and missed actions.