How do I make custom 404 pages?

I have a page called error.html, which I want the user to see when a 404 or 403 is triggered. I don't want any drupal crap on that page, just the content of error.html. Is this possible? Customerror module can't do it, and inserting the name of my file into the drupal error handling of course doesn't work either because it only accepts drupal pages...

I've been trying to get answers to this since september 2010 and so far I've just been ignored, so any pointers would be helpful at this point!