larmaid - I have a script on my web proxy which reboots every 24h so I never have problems with anything hehe
incomm - I have a network of approx 100 users so I manualy set every user to use proxy's (Internet explorer - use proxy server x.x.x.x port 8080)
If you have biiig network, I won't recomend this cause it is time consuming, also when clients format their pc's you have to teach them how to put proxys, so it would be simpler to use transparent proxy, read the instructions on
http://www.mikrotik.com
If you do prefer manual usage, just block tcp port 80 like this:
/ ip firewall rule forward
add src-address=10.0.0.0/24 dst-address=:80 protocol=tcp action=drop \
comment="Drop port 80 for everybody" disabled=no
if you do want to enable any client to use port 80, you just put one action=accept before this which blocks everybody
add src-address=10.0.0.22/32 dst-address=:80 protocol=tcp action=accept \
comment="Accept port 80" disabled=yes
see ya