http://www.w3.org/Style/CSS/current-work.html http://www.w3.org/Style/CSS/current-work.html As you can see CSS3 is very far from being "finalized" so any imple

http://www.w3.org/Style/CSS/current-work.html http://www.w3.org/Style/CSS/current-work.html As you can see CSS3 is very far from being "finalized" so any implementation that mozilla or webkit or someone does is just their best guess at what the final standard will be or experiments to provide recommendation. They leave the prefix free version for when they actually know what it is they are implementing to cause less pain in the long term allowing developers to know full well that what they are using is far from finished.