I apologize if I missed it somewhere else, but how do you specify that the content on each slide in an S5 slide show should be vertically centered?

I don’t know of a totally robust way to do it. My CSS-fu is weak.

But

Test Vertical Alignment
------------------------

This is centered on the slide
{: style="margin-top:25%;text-align:center;}

is a pretty good approximation to what you want.