It works on browsers that are up-to-date with those technologies, but not on older browsers.
I have seen previous versions of this page working in Firefox and Netscape 6.1 on the Mac, Windows, and Linux, in Internet Explorer 6 and 7 on Windows, and in Internet Explorer 5 on the Mac. Also: Opera 9 on each OS, and Chrome and Konqueror on Linux.
The most serious limitation is that the time it takes to load is greatly influenced by the number of pixels in the canvas (which is a DOM table). A comfortably roomy canvas takes minutes to load on my computer. So the advantage of lightweightness is lost if the canvas is large. (Note: Firefox is the worst loser here. At size 100×100 it takes 4 seconds to load on my D420. Opera and Konqueror load it in less than half that time.)