This is an interactive periodic table (chemistry reference table).
I created this periodic table in 2007, mainly as an experiment in CSS, JavaScript, SVG, and XML transformation with XSLT. It's a bit awkward behind the scenes, but the presentation came out well, in my opinion, and the interactivity is awesome. I hand coded the whole thing. It works well in Chrome, Safari, and Firefox. Not so much in IE, although with IE8 it does work slowly.
At the time, I could not find a ready-to-use XML source for the elements and their various properties. I could not even find a traditional database source. So I spent a long time accumulating the data from various sources, including Wikipedia and many others. I am happy to provide these XML files to anyone interested: