Everybody wants to use CSS 3 now that even Internet Explorer will support parts of it once IE 9 is out. But since parts of CSS 3 are still subject to change, most browsers use a vendor prefix for many CSS 3 properties to signal that their implemenation is “experimental� and may change in a later version of the browser.
This means that for a property like border-radius to work cross-browser you need to specify it several times with different vendor prefixes, like this:
.box {-moz-border-radius:10px;-webkit-border-radius:10px;border-radius:10px;}