Mike Bostock's Blocks

Bl.ocks (pronounced “Blocks”) is a simple viewer for sharing data visualization code examples hosted on GitHub Gist created and run by Mike Bostock. The main source for your example is in index.html. This file can contain relative links to other files in your Gist, such as images, scripts or stylesheets. And of course you can use absolute links, such as CDN-hosted D3, jQuery or Leaflet. To explain your example, add a README.md written in Markdown. (You can omit the index.html if you just want to write, too.)