Many CSS3 attributes (e.g. border-radius) have long been implemented in various browsers with vendor prefixes, such as -moz and -webkit, which allow browser vendors to work on implementations of new features before the standard notation is set in stone.
Remembering the different prefixes and the sometimes ridiculous variations in syntax for the attributes is a pain. Fortunately, Nettuts+ has made a nifty web utility that analyzes your CSS and adds in extra rules with the vendor prefixes. You just need to write your CSS with either the official attribute or one of the prefixed versions, and Prefixr will do the rest for you.
It can even minify your CSS for you. (Though Mac may users may also want to try Minimus for that.)
If that wasn’t cool enough for you, it even has an API. You could use this to create your own tools that make use of Prefixr, or you could use it to integrate it with your favorite text editor. Examples are included for Textmate, Vim, Espresso, Alfred and Coda. And someone has already cooked up a Text Filter for BBEdit. That’s the killer feature for me. I can just hit a keystroke in BBEdit and the text updates a second later.
Cross-Browser CSS in Seconds with Prefixr [Nettuts+]