@Oldpilot: <mbp
agebreak> is kindle specific. The correct way to specify page breaks in html is
<div style="page-break-after:always"></div>
You should also read the conversion section of the calibre user manual to learn how to control where calibre puts its automatic pagebreaks.
@wn0x: If your input document contains font families they will be in the output stylesheet as well, unless what you put into extra css overrides them. In that case, Tweak epub is the way to go.