Your question is vague, tell us more about why you're considering
using Squid in the first place. What is your goal here, what problems
are you actually trying to solve?
I've never tried it, but I think normally you would never
want to cache pages served from OpenACS by default in Squid, as many
pages are customized for the user viewing them, and Squid presumably
has no way to distinguish one OpenACS user from another. On the other
hand, cacheing images or static content in Squid might be useful for
some sites. (It might however be better just to serve that content
separately with a different special purpose web server in the first
place. The guys using AOLserver at AOL definitely do that.)
OpenACS uses AOLserver to cache all sorts of stuff, but it is probably
all stuff a lower level than complete HTML pages, and then is used to
assemble dynamically generated pages, which would make pretty distinct
from anything you'd ever consider caching with Squid.
I think AOLserver's Fastpath code will cache the contents of static
files in RAM, which would overlap to some degree with
Squid-like cacheing, but I don't know whether Fastpath even works with
OpenACS.