htaccess - custom error pages

How would I program an htaccess file to jump to an error page, whenever users access a non-existant document?

There is a good tutorial at:

http://javascriptkit.com/howto/htaccess2.shtml

You would create something like:

ErrorDocument 400 /errors/badrequest.html
ErrorDocument 401 /errors/authreqd.html
ErrorDocument 403 /errors/forbid.html
ErrorDocument 404 /errors/notfound.html
ErrorDocument 500 /errors/serverr.html

as your htaccess file and when you get the specific error it sends you to the link e.g.
a 400 error would send you to the page /errors/badrequest.html

I've read that site word by word, and whenever I try adding ANY content to the access doc, it says "internal server error"