Anyway... I want to serve up from simple content over the web from my Raspberry Pi, so I thought, I know the tool for that - lighttpd (aka lighty)!
Unfortunately when I tried to install it I was faced with an error (pretty unusual in my experience of using apt-get) which stated:
How annoying, anyway a little bit of research suggested that the group www-data doesn't exist on the Raspberry Pi distro of Debian, and hence why it was failing. A pretty easy fix - add the group "www-data" and re-run the install.
That was it, worked like a charm!