Although the first stage of the Web's development was primarily visual in nature, the need to provide web content in other media led to the introduction of medium-specific styling in CSS. The ability to take the same document and customize its presentation in a manner best suited to different output media is deeply powerful. Although the most common use for this power will be to create "printer-friendly" styles for documents, we've also seen how projection styles can be used to create slideshows with Opera.
While aural styles would be very useful for blind users, as of this writing, there are only two programs that support even a fragment of this portion of CSS, and the media type aural defined in CSS2.x will not be carried forward to future versions of CSS. Instead, the media type speech has been set aside for future work in auditory rendering of documents.