What is a 404 page redirect URL and what are the set up options?

Short URLs = custom domain + short hash (myshortdomain.com/obza4). If a visitor makes a mistake in the short hash, by default it will go to a TINY/not found (404 error page). 404 page redirect option means that a separate "error" page can be configured so that link mistakes (instance of any short hash error) will go to the page of your choice.

To set up a custom 404 page, login to your account and go to: Domains > Domain Settings > 404 page redirect.

Enter the custom 404 URL into box: "404 page redirect URL" (such as http://mysite.com/faq/landingpage.html ).

NOTE: The destination of 404 page redirect URL can't be the same as your custom domain. Don't use your custom domain for this setting or it will result in an endless loop error.