404 Configuration

I have been dropped in to a large site, and I have found myself
administrator of one of its subdomains. I have been instructed to
close the public facing side, while leaving the intranet open.

So, let us say I'm part of www.oursite.com. I am administering
www.myspot.oursite.com. The intranet is located at www.myspot.oursite.com/Intranet,
and there are further subdomains such as
anotherspot.myspot.oursite.com. It seems ownership of the overall
site and the various subdomains has been passed on from person to
person for a while now, and consequently I am having a lot of trouble
finding assistance from my higher-ups.

So, I am here with my problem...

The material on the public facing site has been backed up in several
places, and my intention was to delete the obsolete material -
basically, everything except /Intranet - from the server. I wanted to
modify the 404 settings, so any 404 error would send the user to the
new index, which would announce the closure, provide alternative
links, and, after 15-30 seconds, auto-forward to the new subdomain
which is replacing the obsolete materials.

The information I found in the manual pointed me to .htaccess files,
which I could not find at either the site root or inside any folders.
In the server's /conf folder I found an number of configuration files
which seemed to have the setting I wanted, and so I did the following:

#
# Customizable error responses come in three flavors:
# 1) plain text 2) local redirects 3) external redirects
#
# Some examples:
#ErrorDocument 500 "The server made a boo boo."
ErrorDocument 404 https://www.myspot.oursite.com/index.html
#ErrorDocument 404 "/cgi-bin/missing_handler.pl"
#ErrorDocument 402 http://www.example.com/subscription_info.html
#

I made this edit to both httpd.conf and httpd.conf.php (after backing
them up) and uploaded them to the server. There has been no change.

Obviously I am missing something, but I am unable to find what it
might be.
Do I need to reboot or reset the server?
Am I editing the wrong files?
Are my edits being overwritten by a higher-level server, such as
whichever administers to the root www.oursite.com domain?

Any help or hints would be appreciated.

Regards,
Ben Rebach