Earlier quoted context omitted.
The company responsible seems to have responded in the comments: "It was definitely a mistake on our part. The problem was not the encoding on our data feed, but the HTML document was sent with ISO-8859-1. The second we inserted the twitter text into the DOM, the browsers interpreted the UTF-8 string as ISO-8859-1. Our visualizations are hosted on other platforms, and in this case the server was not configured to sen…
Including is like the first thing you do when starting front-end development. Every time you don't validate...God kills a kitten. Please, think of the kittens. This has been a Public Service Announcement. Please code responsibly: http://validator.w3.org/