CSS: The Definitive Guide, 4th Edition

Chapter 2. Selectors

One of the primary advantages of CSS is its ability to easily apply a set of styles to all elements of the same type. Unimpressed? Consider this: by editing a single line of CSS, you can change the colors of all your headings. Don’t like the blue you’re using? Change that one line of code, and they can all be purple, yellow, maroon, or any other color you desire. That lets you, the designer, focus on design, rather than grunt work. The next time you’re in a meeting and someone wants to see headings with a different shade of green, just edit your style and hit Reload. Voilà! The results are accomplished in seconds and there for everyone to see.

Basic Style Rules

As stated, a central feature of CSS is its ability to apply certain rules to an entire set of element types in a document. For example, let’s say that you want to make the text of all h2 elements appear gray. Using old-school HTML, you’d have to do this by inserting <font color="gray">…</font> tags inside all your h2 elements. Using the style attribute, which is also bad practice, would require you to include style="color: gray;" in all your h2 elements, like this:

<h2><font color="gray">This is h2 text</font></h2>
<h2 style="color: gray;">This is h2 text</h2>

This will be a tedious process if your document contains a lot of h2 elements. Worse, if you later decide that you want all those h2s to be green instead of gray, you’d have to start the manual tagging all over again. (Yes, this is really how ...