Many thanks to w3schools.com for excellent tutorials in HTML, Javascript, CSS, PHP and much more which I haven't had time to study yet.
The sound files and help screens are adapted from the Countdown game by Loz Archer (male or female I know not). Check out http://loz.the-pub.org/games/.
The letter frequencies for the letters game are taken from The Countdown Corral at www.thecountdowncorral.com/cd/.
The word list used to validate words and pick conundrums is the ENABLE list which I got from http://personal.riverusers.com/~thegrendel/.

Please note this site has no connection with Channel 4 or Yorkshire Television, who make the programme.

Technical stuff
The site was developed at a screen resolution of 1024x768, but pages generally have a width less than 600, so can be run quite well at lower resolution.
Pages have been tested with Internet Explorer 6 & 7, Firefox and Opera browsers. Opera shows a problem with the sizing of the letter boxes and the letter piles. I may fix it one day.
The sound may be turned on and off via the control in the upper right. Sound files are all .swf (Flash) files. Adobe claim the Flash player is installed in 90%+ of browsers. If you need to download it, you'll find it on the Adobe site at www.adobe.com.

The official Countdown web site is at www.channel4.com/entertainment/tv/microsites/C/countdown/
The Countdown Page on the web (www.thecountdownpage.com) has almost more information than you would ever want about Countdown, and has lots more links to Countdown related stuff.

If you have any comments, complaints, suggestions etc. please mail here.