The biggest difference between CSS2 and CSS3 is that CSS3 has been divided into different sections called modules . Each of these modules goes through the W3C at different stages of the recommendation process. This process has greatly simplified the adoption and implementation of CSS3’s various components in the browser by various vendors.
If you compare this process to what happened with CSS2, where everything was presented as a single document with all the cascading style sheet information, you can see the benefits of separating the recommendation into smaller, separate parts. Because each of the modules is designed individually, developers enjoy a much wider range of browser support for CSS3 modules.
Features in CSS3 not included in CSS2
CSS3 has many additional features that CSS2 didn’t include, including:
CSS template layout module and CSS3 Grid positioning module : Create grids using CSS.
Text module CSS3 : Highlight text and even create shadows with CSS.
CSS3 color module : now with opacity.
Block model changes : including a marquee property that acts like an IE tag.
CSS3 UI module : gives you new cursors, action responses, mandatory fields, and even resizes elements.
Media queries : Media queries provide more flexibility in determining how a style sheet should be used. For example, you can define a style sheet that is only for portable devices with a viewing area greater than 20em.
CSS3 Ruby module : Provides support for languages that use ruby text to annotate documents.
CSS3 Paged Media module : for even more support for paged media (paper, transparencies, etc.).
Generated content : running headers, footers, footnotes, and other content that is generated programmatically, especially for unloadable media.
CSS3 Speech Module : Changes to sound CSS.