I know that if we want to make sure some CSS3 features work everywhere we need to use the prefixed versions of the W3C recommended one like:
transition: all 1s ease;
-moz-transition: all 1s ease;
-o-transition: all 1s ease;
-webkit-transition: all 1s ease;
I know that the prefixes are used for experimental features, but why are they necessary? Why don't they test them on the original W3C one? Does every CSS3 feature has or had a prefix for every browser or they just create a prefixed version if they think they should?