Thanx for the tip, there is an interesting IE hack there, but neither of those pages handle vertical centering.
I could use one of the tricks, also mentioned in an earlier post to put the element at 50%, and then set the margin negative to half the size of the content (i.e. -200px for an element that is 400px high), but that would require fore-knowledge of the content size, something that is not necessary for say: "text-align: center".