I've found that using em to indent paragraphs with different font sizes is no good. For example, I like to use blockquotes for long quotations and use a smaller font size so that it stands out. I also like to use smaller font sizes for footnotes. In this case the indents would not align between the two paragraphs, especially if whole numbers are all that is allowed for ems. You have to use pixels in that case.

Does KindleGen allow non whole numbers for font size em specifications? For example, font-size: 1.2em; .