We have a Force.com domain say my-domain.force.com and several sites there. I know that you can set error pages for each of those sites for example you can display your own page when someone will try to access my-domain.force.com/mysite/[unexisting page].
But can you somehow set or change error page for your Force.com domain which will be displayed when you try to access my-domain.force.com/[unexisting site]? It is strange that I can`t find the page that is currently displayed in this situation in my org. It shows page that one of our sites is under construction but we do not have such a page now.