And, in order to have the text centered in the
screen, you have to somehow set the height of the <div> in #1 to 100% of the available screen space (i.e., discounting margins, status bar, etc.). While "height: 100%" looks perfect for that, it's behaviour is actually undefined, or at least in practice it is. Setting the height of <html> and <body> may do the trick in some cases, but not all. This is the reason why it is not possible to do this in ePub in a portable way.