Margins: % or em ?

[odamizu]

My source material is EPUB, which I then convert to dual-mobi via Calibre.

I typically set top and bottom margins around chapter heads. I used to use %, then discovered this resulted in missing chapter heads and text in the mobi portion (though the kf8 portion is fine). Switching to em solved this problem.

When I looked in the Kindle Publishing Guidelines, I found: "When using the margin and padding CSS properties, specify the values in percentage (%) instead of em units" (section 3.1.7 on page 15).

Does anyone here use % with margins such that it works with both mobi and kf8? Any idea what I might be doing wrong?

Examples

Spoiler:

This results in missing chapter heads and text when converted to mobi (but works fine in kf8):

h1 { 
font-size: 120%; 
margin-top: 20%; 
margin-bottom; 10%; 
text-align: center;}

But if I change it to em, it works for both mobi and kf8:

h1 { 
font-size: 120%; 
margin-top: 2em; 
margin-bottom; 1em; 
text-align: center;}

[phillipgessert]

I usually use % for margin-top and ems for margin-bottom. This gets me closest to the way I'd have designed for print, and I haven't run into any problems yet.

[odamizu]

Thanks phillipgessert! I will experiment now that I know % can work.

[odamizu]

Looks like this is a Calibre issue rather than a mobi problem. When I tried KindleGen, everything works fine. I started a new thread in the Calibre forum: https://www.mobileread.com/forums/sho...d.php?t=269358

Thanks for pointing me in the right direction.