If I got it right, despite there is no explicit proxy set up for konqueror, there is a transparent proxy running on tjener (the main server). Now, we want to prevent pupils from visiting non-paedagogic web pages (we did this before, so we have the blacklist and an old squid.conf). My first try was to configure /etc/squid.conf on the ltsp server that serves the thin clients. This didn't show any effects. Did I make some mistake, or was it just the wrong place?
Any URL to the corresponding section in the manual should do, a precise instruction won't be refused, of course :) Thanks cya Ralf

