[jhowell]

Originally Posted by Turtle91

ePub 3.3 standard:

6.3.1.3 "Prefixed properties"
...
The prefixed properties are documented in E. Prefixed CSS properties.

While I agree with your stance on property names that begin with "-webkit-" and other prefixes, if you look at the cited appendix it becomes clear that "Prefixed properties" in this case refers to property names that begin with the "-epub-" prefix.