I'm wondering if it's possible to use mod rewrite along with the ErrorDocument deceleration to customize the error pages depending on what type of file is requested.
For example a non-existent html or php file is requested Apache will give nice custom HTML page.
But if a non-existent image, js, css, etc... file is requested then Apache will serve out a basic html file with only a link on it.
A good example of this behavior is Facebook. Try requesting a bogus JavaScript file, you will receive a different page then if you were to request a non-existent php file.