I believe you want the text to follow the semi circle, and not just have an ordinary align left along a straight edge. This is not (yet) possible with a simple css property. There are some hacky techniques like this however: http://www.torylawson.com/mw_index.php?title=CSS_-_Wrapping_text_around_non-rectangular_shapes
There are even a tools to help you, like this one: http://www.csstextwrap.com/
Adobe is pushing a new css property to wrap text: http://www.adobe.com/devnet/html5/articles/css3-regions.html
It should be already available in Chrome Canary, but I suppose that is of little use for you today. I think you will have to do with a hack today...