Trying to debug an issue with em-dashes, I came across this relatively old (2001) but extremely useful article at A List Apart on em dashes, en dashes, and other typographic issues in Web design (which could be subtitled "The Web is Not a Typewriter") that's probably useful reading for anyone attempting to do good Web design.
Other Punctuation
Many people (most, from what I’ve observed) believe that curly single opening and double opening quotes are the correct symbols for feet and inches. If you are one of these people, put out your hand so I can slap it with a ruler.
The correct symbols to use are prime and double prime. They look similar to curly quotes in a few fonts, but are usually much more distinct. They never, ever look like commas. They are usually set at a slight angle of 75—80 degrees, and are also usually tapered from the top to the bottom.
A single prime is used to represent feet or minutes (′ not in HTML 4.01), while a double prime is used to indicate inches or seconds (″ not in HTML 4.01). (I won’t make you learn about the triple prime and the three reversed versions of these characters.)
Also has useful info about changes in typography in HTML 4 and problems in common guides to HTML regarding typography.
Posted by johndanseven at May 16, 2006 12:39 AM