[Izaan]

Can we achieve centering horizontally and vertically but with no predefined height with pure CSS/XHTML?

[SaswatPadhi]

Do you want something like http://pmob.co.uk/pob/vertical-center1.htm ? When you re-size the browser, it automatically centers itself.

If you want something like that, take a look at this tutorial : http://pmob.co.uk/pob/hoz-vert-center.htm.