iceweasel 10.0.12 (basically the same as Firefox 10.0.12)
It ships as the default browser for debian wheezy.
The home page of flotcharts.org does work correctly.
I also tried Konqueror Version 4.8.4 (KDE's browser) and it didn't even display the graphs (not in the blog post or on flotcharts.org).
http://www.flotcharts.org/
If not, what browser are you using? It would be nice to know if Flot is not compatible with something.