2.7 Summary

By using selectors based on the document's language, authors can create CSS rules that apply to a large number of similar elements just as easily as they can construct rules that apply in very narrow circumstances. The ability to group together both selectors and rules keeps style sheets compact and flexible, which incidentally leads to smaller file sizes and faster download times.

Selectors are the one thing that user agents usually have to get right because the inability to correctly interpret selectors pretty much prevents a user agent from using CSS at all. On the flip side, it's crucial for authors to correctly write selectors because errors can prevent the user agent from applying the styles as intended. An integral part of correctly understanding selectors and how they can be combined is an understanding of how selectors relate to document structure and how mechanisms—such as inheritance and the cascade itself—come into play when determining how an element is to be styled. This is the subject of the next chapter.