View Source to see how this rounded corner example is put together. No images are used in modern, CSS3 compatible browsers. The technique is explained in detail in our css round corner article.
I'm pure CSS3 for maximum simplicity and speed in Firefox and Safari, but I still look good in IE7 and above! Thanks to the magic of conditional CSS and a small bit of extra markup, it all comes together. In IE6, I look square, but IE6 users, a dwindling breed, are used to ugliness.
Many additional examples of rounded corner divs and buttons created with CSS3 but backwards compatible with IE are found on the BestInClass.com site.