Non-Existant Page gets HTTP 200 and not HTTP 404: Why?

I want to create a custom 404 page with:

ErrorDocument 404 /errordocs/404.html

Code (markup):

In trying it out, I tried testing it with a non-existant page, http: //localhost/page_not_exist.html, but it did not go to /errordocs/404.html.

So I checked out the access.log, and fake page_not_exist.html did not get the expected HTTP error 404 but instead got HTTP accepted 200, and then the localhost site got redirected to the default /index.php!

127.0.0.1 - - "GET /page_not_exist.html HTTP/1.1" 200 66039
127.0.0.1 - -  "GET /index.php?=PHPE9568F34... HTTP/1.1" 200 2524

Code (markup):

Why would this happen?

Jeff in Seattle