The "ceiling" symbols (left/right square bracket upper corner) at the beginning of the explanatory text are displayed as unknown character boxes here (Win7/Chrome).
I'm not the OP but did a little looking at the source. It's encoded as UTF-8 and is rendering fine in Chrome on Mac. Can someone more experienced with Character Encoding chime in? I've always wanted to learn more about how things like this happen. (I assume it's a character encoding issue?)
Not really an encoding problem, I suppose the issue arises because the fallback font does not have those symbols. I can't test on Windows but if someone could point me to a font which has those mathematics characters on Windows I'll gladly specify that font.
The browser is supposed to find a font that does have them in that case, so I guess no font does. Ssame on iPad.
Can you point me to something that shows this? I know font family declarations with multiple fonts will fall back but I've never heard of this before. FWIW, the site only declares one typeface "Lucida Grande" so I assume to browser is falling back to the default Sans-serif on windows.