This might be a newbie question but any help is appreciated.
If a visitor types in: example.com/blahblah
And "blahblah" doesn't exist, how do I get it (or other mistyped extensions) to be redirected to a page that says "The page you typed in doesn't exist but please go to example.com"
I've seen that on many sites but don't know how that is done. Thank you.