[squid-users] Flags in log file

I would like to know the differences between the following flags in my Squid
access.log file:

        TCP_HIT
        TCP_MEM_HIT
        TCP_CLIENT_REFRESH_HIT

Where can I find more info about these flags? Also, is there anyway to find
out that the page loaded into the browser is not cacheable (on web server's
request)?

Thank you for any info.

-- 
Subba Rao
subba9@home.com
http://members.home.net/subba9/
GPG public key ID 27FC9217