Apparently if the character is not in your font set, they won't appear
Your font set can be pretty inclusive. I read the font matching algorithm as saying that if a given character isn't found in one font, then the browser will look for that character in the next font.
In particular, although I may be wrong, I'd kind of expect the generic fonts like "serif" and "sans-serif" to support the standard entities; and so I'd guess you're safe if you include a generic font at the end of your font set.
ChrisW
2009-08-13 23:08:51