A processing device in a system can receive a definition and an assigned value for a global variable for an on-line document such as an HTML document, and a definition of a component variable associated with a component of the on-line document. The component variable is defined so as to acquire a globally specified value, such as the value of a globally specified variable. The definition of the global variable and the definition of the component variable are stored in an aesthetic descriptor file such as a cascading style sheet configured to refer to the assigned value for the global variable and the globally specified value for the component variable when rendering the on-line document. The descriptor file can then include two tiers of variables with values that are globally assigned, providing granular control to authors.