Look ma, those drop shadows are breathing!
Your eyes want you to believe that the blocks are hovering up and down, when in fact only the drop shadow is being translated out and in again.
Follow me on https://twitter.com/cpbotha for even more fun, or see my other d3 blocks:
Modified http://d3js.org/d3.v3.min.js to a secure url
https://d3js.org/d3.v3.min.js