Already, alternative web navigation devices are on the market, offering much more variety and capabilities than was common in the past. This crucial fact was recognized in the creation of CSS2, and the expectation is that the variety of rendering platforms for CSS will only grow as time goes by. CSS2 now allows for the targeting of style rules to specific media types. This means you can explicitly request that one or more style rules will only apply when rendering to certain device types, such as a printer, an aural browser or a handheld device.
Some property values have different meanings in different Media contexts.
At-Rule syntax specifies the target media for an imported style sheet. The following list of Media type keywords is given in the CSS2 spec, and that same spec also does not consider this list to be definitive. If a browser claims to support a specific media type, it should implement all of the CSS properties that the CSS spec should apply to the indicated media. All May be rendered using any media-type device. Aural Rendering targeted for speech and sound synthesizers.