Every now and again when I am browsing the net I get the message "Cannot find server or DNS Error" when I know for a fact that the website I am trying to reach does exist.

These problems (this one and the MTA) sound like either a connectivity problem between your machine and the DNS server (possibly a timeout, even) or a configuration problem with the DNS server (e.g., reverse lookups aren't being handled). We'd have to know a bit more about your configuration to say more. Where is the DNS server? What DNS server software does it run (BIND, tinydns, etc.)? What's /etc/resolv.conf look like on the machine with the browser? Daryl