@Bald Eagle,
Just to fool you, neither of the above

Try something like these instead:
Code:
@font-face {font-family: "Charis"; font-weight: normal; font-style: normal; src: url("res:///fonts/normal/Charis SIL Compact")}
@font-face {font-family: "Charis"; font-weight: bold; font-style: normal; src: url("res:///fonts/bold/Charis SIL Compact")}
@font-face {font-family: "Charis"; font-weight: normal; font-style: italic; src: url("res:///fonts/italic/Charis SIL Compact")}
@font-face {font-family: "Charis"; font-weight: bold; font-style: italic; src: url("res:///fonts/bolditalic/Charis SIL Compact")}
where the
blue label matches whatever you've put in your css class and the
red name matches
exactly the
internal filename of the font family.
When you add new fonts to user memory /fonts (i.e. /mnt/onboard/fonts) and then reboot, the Kobo "does stuff" with the contents of the fonts directory and holds the data somewhere else internally.