Re: [CSS3 box] Proposal: content-align

> text in an inner box with a specified width and setting its
> margin-left and margin-right to "auto". Left and right alignment
 
> There is no such thing for vertical aligment. Perhaps, given a
> container with a specified height, the same rules could be introduced
> for margin-top and margin-bottom?

Actually, there is:  you need to absolutely position the inner box with
top, bottom, left and right 0 and all margins auto, after making the outer
box a positioning context.  However, the problem that I thought was being
raised here was the case when you didn't know the height of the inner box.