Vertical align div in XHTML 1.1 for EPUB?

I have been Googling this and find many entries on it, most of which use table-cell like this:

http://www.vdotmedia.com/blog/vertically-center-content-with-css/

They work fine, but why I change the DOCTYPE to XHTML1.1, which I need for an EPUB page:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">

It no longer works. Am I out of luck? I have blocks of text that vary in length that I would like to vertically center on a page in an epub reader such as iBooks (which are based on WebKit -- I do not need to worry about other browsers).

Solution

There's another trick you can try.

If you have this structure:

<div class="container">
    <div class="text">
    Some text you need aligned vertically
    </div>
</div>

On the CSS you'd have:

.container {
    height: 50px;
    position: relative;
}

.text {
    position: absolute;
    top: 50%;
}

You can give that a go if you'd like. Change the height to whatever you need it to be of course.