This is certainly more detailed than mine but I also have a blog post (http://lifebeyondfife.com/87-beauty-html/) documenting three different methods and the JavaScript code to make these in an HTML5 canvas on GitHub: https://github.com/lifebeyondfife/Sierpinski.

EDIT: After going back for a further look, saying that the original link is more detailed than mine doesn't do justice to the amount of content (images, animations, code, explanations) there actually is.