I got currently an problem with SMALL CAPS: They don't function in my ereader (built 2015/16, so I assume in other ereaders is the same) - CSS font-size does. In calibre File Preview they function both.
SMALL CAPS vs font-size: 0.75em;
Code:
span.small_font {font-size: 75%;}
75% (or 0.75em) works fine with the surrounding characters (in ereader). But it's
not exactly SMALL CAPS.
What do you think about!?