Thanks to everyone who responded to my experimental Protovis post*, whether in the survey, via twitter or in comments on the post. It quickly became clear that my trick for including the code to generate the chart completely failed to work in Chrome and Safari browsers. I still do not fully understand why that is, but I have now worked out a completely different approach to the problem which (fingers crossed) seems to work in more browsers, although I still cannot vouch for all versions of Internet Explorer.
So here is the chart one more time. I hope it now works for (almost) everyone!
I will also be updating the howto post very shortly to explain my new technique.
UPDATE: at the moment, this trick is not working on mobile devices. It should now be working on mobile devices except for Android. The only remaining problem is IE, but I think that will not be possible. I will instead try to make it fail more gracefully on IE.