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This looks like it should be possible with the following:
.verticalText
{
/* IE-only DX filter */
writing-mode: tb-rl;
filter: flipv fliph;
/* Safari/Chrome function */
-webkit-transform: rotate(270deg);
/* works in latest FX builds */
-moz-transform: rotate(270deg);
}
This works in IE.
It goes wrong in a bizarre way in Safari, Chrome and FX - the cell's size is calculated before the text is rotated!

Here is a demo: http://jsfiddle.net/HSKws/
I'm using dynamic images as a workaround, although that also has its problems. I'm happy with that as a fall-back, but it seems like there should be a way to make this CSS work - it's almost there.
Anyone know a way to make the cells fit the content after the transform has been applied?