The browsers themselves will do caching to speed things up if you return to a page. You can clear it out from the browser. There are also temporary files in /tmp that could be cleared out. It might be best to do it before shutting down. For example, log out of KDE or Gnome and log into a terminal. Then su to root and enter run level 1:
init 1. Now it should be safe to remove all files from the /tmp directory: rm -r /tmp/*
before shutting down: shutdown -h now
You could also add it to a shutdown script. The best place may be in /etc/init.d/halt.local.
Code:
#! /bin/sh
#
# Copyright (c) 2002 SuSE Linux AG Nuernberg, Germany. All rights reserved.
#
# Author: Werner Fink <werner@suse.de>, 1998
# Burchard Steinbild, 1998
#
# /etc/init.d/halt.local
#
# script with local commands to be executed from init on system shutdown
#
# Here you should add things, that should happen directly before shuting
# down.
#
rm -r /tmp/*
