If you mean the software used to make it, I would assume Adobe Dreamweaver or something like that. The standard markup language for webpages is however HTML.
@Plasmoid(View Post) The forum software is a custom one written by Simon, I think. It's PHP-based, JQuery and Twitter Bootstrap front-end. @therocketeer(View Post) You actually lose out on the most advanced parts with a GUI editor. The code for this looks hand-written, the breadcrumb and forum posts are generated by respectively JQuery and PHP/JQuery. Most of the looks are from Twitter Bootstrap anyways.