I know you\'re thinking that this is a strange request, however I am currently dealing with a client that gave me a template and decided he wanted it 70% smaller after seeing it
You might be able to use the CSS Zoom property but negativly? - supported in IE 5.5+, Opera, and Safari 4, and Chrome (verifed, please check before downvoting).
Firefox is the only major browser that does not support Zoom (Check here) but you could use the "proprietary" -moz-transform property in Firefox 3.5.
So you could use:
div.zoomed { zoom: 70%; -moz-transform: scale(.7); }