A 404 bug ?

I was trying to customize 404 error page at https://webtips.blogsome.com Though am not a very techy guy but I managed to find a way out https://webtips.blogsome.com/2006/11/19/customize-404-page-free-blogs/ (Any suggestions are welcome)

But when I typed https://webtips.blogsome.com/2006/11/19/customize-404-page-free-blogs/404 (replace the URL with any post URL and 404 with any numerical figure) I got everything except the post content!

I tried with quite a few blogs and I got similar results. Some blogs returned me the exact post page. I am not too sure but I think I should have got a 404 error page instead.

Thanks