One of the most important features of style sheets is that they 
specify how a document is to be presented on different media: on the 
screen, on paper, with a speech synthesizer, with a braille device, etc.
here are currently two ways to specify media dependencies for style sheets:
- Specify the target medium from a style sheet with the @media or @import at-rules.
 
- Specify the target medium within the document language.
 
The @media rule:
An 
@media rule specifies the target media types (separated by commas) of a set of rules.
Following is the example:
<style tyle="text/css">
<!--
@media print {
    body { font-size: 10pt }
  }
  @media screen {
    body { font-size: 12pt }
  }
  @media screen, print {
    body { line-height: 1.2 }
  }
-->
</style>
 | 
The document language:
In HTML 4.0,  the 
media attribute on the LINK element specifies the target media of an external style sheet:
Following is the example:
<style tyle="text/css">
<!--
<!doctype html public "-//w3c//dtd html 4.0//en">
<html>
   <head>
      <title>link to a target medium</title>
      <link rel="stylesheet" type="text/css" 
   media="print, handheld" href="foo.css">
   </head>
   <body>
      <p>the body...
   </body>
</html>
-->
</style>
 | 
Recognized media types:
The names chosen for CSS media types reflect target devices for which
 the relevant properties make sense. They give a sense of what device 
the media type is meant to refer to. Following is the list of various 
media types:
| Value | Description | 
| all | Suitable for all devices. | 
| aural | Intended for speech synthesizers. | 
| braille | Intended for braille tactile feedback devices. | 
| embossed | Intended for paged braille printers. | 
| handheld | Intended for handheld devices (typically small screen, monochrome, limited bandwidth). | 
| print | Intended for paged, opaque material and for 
documents viewed on screen in print preview mode. Please consult the 
section on paged media. | 
| projection | Intended for projected presentations, for 
example projectors or print to transparencies. Please consult the 
section on paged media. | 
| screen | Intended primarily for color computer screens. | 
| tty | Intended for media using a fixed-pitch character 
grid, such as teletypes, terminals, or portable devices with limited 
display capabilities. | 
| tv | Intended for television-type devices. | 
NOTE: Media type names are case-insensitive.
 
 
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