I have created lots of epubs, but don't have much experience with .mobi. I converted an .epub to .mobi using Calibre. In the Kindle Previewer, it looks fine for Kindle, and Kindle DX, but for iPhone and iPad, all the text is tiny and scrunched together on top of itself, completely unreadable. Do you think there is something wrong with the file/css or is this a previewer problem?
