I've just noticed that on a couple of our sites a bad address just gives a standard browser 404, so it appears the page not found handler is not working for some reason.
This is .Net 4.5 with integrated pipeline app pool on Server 2008R2. mojoPortal 220.127.116.11 (and a couple of other sites on versions close to this, including 18.104.22.168).
I've seen this thread https://www.mojoportal.com/Forums/Thread.aspx?pageid=5&t=4082~-1 and tried the various web.config tweaks, but no joy.
I see there is a custom 404 page on demo.mojoportal.com.
OK... after some more head-banging, it is fixed, using this post https://www.mojoportal.com/Forums/Thread.aspx?pageid=5&t=12792~1
Could that be included as standard, or does it cause bother in some environments?