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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.
Certain CSS properties are only designed for certain media (e.g.,
the 'cue-before''page-break-before' property
for aural user agents).only applies to paged media). On occasion, however, style sheets for
different media types may share a property, but require different
values for that property. For example, the 'font-size' property is useful both
for screen and print media. However,The two media types are different enough
to require different values for the common property; a document will
typically need a larger font on a computer screen than on paper.
Experience also shows that sans-serif fonts are easier to read on screen, while fonts with serifs are easier to read on paper. For these reasons,Therefore, it is necessary to express that a style sheet --sheet, or a
section of a style sheet --sheet, applies to certain media types.
There are currently two ways to specify media dependencies for style sheets:
@importurl("loudvoice.css")aural;url("fancyfonts.css") screen; @media print { /* style sheet for print goes here */ }
<!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>
The @import rule is defined in the chapter on the cascade.
An @media rule specifies the target media types (separated by commas) of a set of rules (delimited by curly braces). The @media construct allows style sheet rules for various media in the same style sheet:
@media print {
body { font-size: 10pt }
}
@media screen {
body { font-size: 12pt13px }
}
@media screen, print {
body { line-height: 1.2 }
}
A CSS media type names a set of CSS properties. A user agent that claims to support a media type by name must implement all of the properties that apply to that media type.The names chosen for CSS media types reflect target devices for
which the relevant properties make sense. The names of media types are
normative. In the following list of CSS media types, the parenthetical
descriptions are not normative. They only give a sense of what deviceLikewise, the media type"Media" field in the
description of each property is meant to refer to.informative.
Media type names are case-insensitive.
Due to rapidly changing technologies, CSS2 does not specify a definitive list ofMedia types are mutually exclusive in the sense that a user agent
can only support one media type when rendering a document. However,
user agents may be values for @media .have different modes which support different media
types.
Note. Future versions of CSS may extend this list. Authors should not rely on media type names that are not yet defined by a CSS specification.
This section is informative, not normative.
Each CSS property definition specifies the media types for which the property must be implemented by a conforming user agent. Since properties generally apply to several media, the "Applies to media" section of each property definition lists media groups rather than individual media types. Each property applies to all media types in the media groups listed in its definition.
CSS2CSS 2.1 defines the following media groups:
The following table shows the relationships between media groups and media types:
| Media Types | Media Groups | |||
|---|---|---|---|---|
| continuous/paged | | grid/bitmap | interactive/static | |
| | continuous | tactile | grid | both |
| emboss | paged | tactile | grid | |
| handheld | both | | both | both |
| paged | visual | bitmap | static | |
| projection | paged | visual | bitmap | |
| screen | continuous | | bitmap | both |
| speech | continuous | speech | N/A | both |
| tty | continuous | visual | grid | both |
| tv | both | visual, | bitmap | both |