All right, I've been beating my head against this for most of the day with no success, so I'm calling in the cavalry - maybe someone here can help! I'm not really sure whether this best classifies as a Sigil or a Calibre problem, but I'll try here first.

Here's my problem: I hand-created an .epub file in Sigil, nothing too fancy - just some chapters and a single stylesheet. Everything looks great in Sigil... but when I try to open the .epub in the Calibre viewer (and subsequently try to convert it to .mobi), it seems to be stripping off all my formatting from my "special" paragraph tags -- any italicized, center-aligned, etc. classes are all made plain and indented on the left, just like my normal paragraphs.

Changing these classes to h1, h2, etc. settings (in other words, replacing a <p class="title"> with an <h2 class="title"> designation) will make the font larger, but doesn't fix the 'stripping' problem (i.e., I just have large text that is still left-aligned and non-italicized).

I've attached the .epub file here in case anyone wants to see the original code. Thanks for any help you can provide!