If you've been around computers awhile, you probably have heard the term ASCII, American Standard Code for Information Interchange. It was limited though, because it only had 256 different letters, which is fine for our alphabet and left a lot of room for accents and glyphs. But, to be practical, we needed more than 256. There are many other alphabets with non-Roman characters. So we went to Unicode, which is 16 bit instead of 8 bit, and that gives us more than 65,000 different characters.
Tom says he's got a problem in Google Chrome on his Mac where he gets squares instead text in the upper right hand corner. And he did it on different computers as well. Leo suspects that he's missing the font that Google is trying to use. Typically there is a fallback font whenever the font that's being used isn't available, and he's checked that Arial is his font substitution.