Basics of the CSS3 Modules
Previous versions of CSS relied on a single specification document to detail all of the features it provided. CSS3 takes a different approach — it relies on the concept of modules to provide the specification. Each module appears in a separate document and details a particular CSS3 feature. This approach provides several benefits:
You don’t have to sift through a huge document to locate the one little piece of information you need.
Each module can be released independently, which means that the standard will be available (in part) sooner.
Specialized groups can work on each module to ensure that it contains the best possible features.
Because modules are smaller, it’s easier to obtain agreement on a standard than to obtain the same agreement for CSS3 as a whole.
At this time of writing, there are fifty modules that could appear as part of a CSS3 standard, but only some of these modules are currently approved — and you really require only a subset of them to create most applications. Here are the essential modules you need to know about in order to work with CSS3 successfully.
Using this set of twelve modules will provide most of the functionality you need for every application. Some of the other fifty modules aren’t even implemented yet (and may never be). For example, the CSS Extended Box Model hasn’t been started yet, but it should provide some exciting new functionality when someone puts it together.
A few of the fifty modules that don’t appear in this list are used for something other than standard applications. The CSS Marquee module is implemented and available, but you normally use it with smartphones.
The groups working on these standards have also combined a few of the modules to make them easier to work with. The CSS 2D Transformations Module and the CSS 3D Transformations Module have been combined into a single CSS Transforms module. So, even though there are three entries in the list, there’s only one implemented module to think about.