Flynn, I apologize in advance for yet another question! I think I'm so inspired by Atahualpa that I can't stop thinking of ways to enhance the website by using it.
I've been reading about improving the user experience by presenting a better 404-File Not Found page. The Codex has a lot about it, and I even found a plugin (Useful 404's) that would help create a better page. But Atahualpa doesn't seem to have a 404.php to edit. I notice that index.php has the "Sorry, what you're looking for isn't here" near the footer. I was able to change that to something a bit nicer, but I didn't hack around any further.
Can we create a 404 page and have it intercept the lost user, and can we customize it via the plugin or by just pasting in some code we find elsewhere, like alistapart.com? And do we need to point to it via the .htaccess file?