You can fully customize your own 404 Error Page on each website. Every new website you create includes a 404 Error page as part of the default pages list. This page is located in the Pages & Navigation window and marked Hidden, so it will nor appear on the site menu.
Tip: You can design your 404 page just like any other page. Create an appealing message so visitors will understand what happened and what they can do next. Need inspiration? You can check our own error page right here.