If you need to make changes to Apache’s httpd.include file on Plesk, your changes will get overwritten. This was driving me mad as I needed to make changes globally, not just on a per-domain vhost.conf basis as is recommended by Plesk. I sent an email to the support department of my hoster, Knownhost, asking where the “raw version” of the httpd.include file was — meaning where was the data for which Plesk was overwritting my changes? My logic was that if I could find where Plesk was pulling this data to overwrite httpd.include, I could modify it to my liking. Andrew from Knownhost told me that the data that overwrites the Plesk config files is hardcoded into the websrvmng binary (this is a utility Plesk uses). Also, Plesk data is strewn about in various databases. Ugh! But, he did offer insight into how to get what I wanted.
The trick is to put your changes in the httpd.conf file which will take precedence over httpd.include (be sure to put it before the httpd.include directive). Well, that was simple. Thanks Andrew and Knownhost!
NOTE: I wrote this post months ago and forgot to post it. In that time I’ve upgraded to Plesk 8.0.1 and I’m really liking it. The above information still applies to Plesk 8, except they’ve moved and renamed httpd.include. No matter, as that file will just be overwritten anyway.