welcome:technical
All of the sub-sites listed on the index page have been written using a combination of HTML, CSS (all valid at last check) and PHP, with a fair reliance on XML for much of the data storage. I'm still learning the latter, so the code may not always be as efficient as it should be, but this is something I intend to improve on with time.
All of this has been done in my spare time. For those of you thinking that I've got far too much spare time, I suggest you examine the dates of the various things that have been posted here. Holding down a full time job, social life and other activities whilst writing and maintaining a small handful of websites is no easy task, I can tell you.