Until Internet Explorer 8 is finally retired we still have to dick about with CSS to make IE behave properly. I’m not a CSS hacker but this is one trick that I suspect I’ll need again at least until IE9 becomes standard.
CSS3 includes a property for rounded corners which was (sort of) adopted in Firefox, Chrome and Safari some time ago. I don’t use it on this site – someone else did the hard work there using images for the corners. Presumably because CSS3 support was so poor at the time. This new CSS3 property can however be retrofitted to old browsers with a little work.