I know rounded corners have come and will probably soon go, but after some searching for a good solution this one by far seems to the best:

http://www.tillett.info/2007/09/11/orb-fluid-css-one-image-round-borders/

My reasons?

1. I think the use of JS for rounded corners is not justified
2. Pure CSS methods add horrible amounts of markup and CSS
3. The traditional 4-image approach is ok but means 4 separate image requests, rather than the 1 that this method uses

I’ve referred to this so many times I thought it would be good to post it here:

http://blog.xkoder.com/2008/07/10/javascript-associative-arrays-demystified/