1. A computer program product comprising one or more computer storage media having thereon computer-executable instructions that are structured such that, when executed by one or more processors of a computing system, cause the computing system to perform the following: an act of evaluating an authored style rule set of one or more authored style rules that apply to a set of one or more markup language element types; an act of deriving a derived style rule set of one or more style rules based on the act of evaluating the authored style rule set; and an act of displaying at least one of the authored style rules of the authored style rule set along with at least one of the derived style rules of the derived style rule set.