You can use something like what's described here.
From that site:
For Webkit and Firefox (as of 3.5),
you can take advantage of the proposed
transform property to handle the
rotation. Each browser requires its
property prefix for now.
-webkit-transform: rotate(-90deg);
-moz-transform: rotate(-90deg);
For IE:
When it comes to effects in Internet
Explorer, there is a surprising amount
of power (and untapped at that, I'd
say) in using filters. Although
misleading, there is a filter called
BasicImage that offers up the ability
to rotate any element that has layout.
filter: progid:DXImageTransform.Microsoft.BasicImage(rotation=3);