Learning XML, 2nd Edition

Properties

The three levels of CSS define so many properties, I can’t cover them all here. There are over 120 in level 2 alone. Instead, I’ll cover the basic categories you are likely to encounter and leave more exhaustive descriptions to books specializing on the topic.

Inheritance

CSS properties can be passed down from a container element to its child. This inheritance principle greatly simplifies stylesheet design. For example, in the document element rule, you can set a font family that will be used throughout the document. Wherever you want to use a different family, simply insert a new property for a rule and it will override the global setting.

In Figure 5-9, a para inherits some properties from a section, which in turn inherits from an article. The properties font-family and color are defined in the property set for article, and inherited by both section and para. The property font-size is not inherited by section because section’s explicit setting overrides it. para does inherit this property from section.

Figure 5-9. Element-inheriting properties

Inheritance is forbidden for some properties where it wouldn’t make sense to pass that trait on. For example, the background-image property, which causes an image to be loaded and displayed in the background, is not inherited. If every element did inherit this property, the result would be a complete mess, with every paragraph and ...