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10.8. Media Types and @-rules

Don't get too excited yet. We aren't talking about media types in the sense of things like audio and video authoring. Well, not exactly, anyway. We're talking about creating rules for presentation within various kinds of media. The defined types of media thus far are:

These are all values of @media, one of several new @-rules. Some others are:

10.8.1. Paged Media

Since I just brought up paged media, I should probably mention that there are some new properties that apply to such media. Five of them apply to page breaks and where they appear:

page-break-before
page-break-after
page-break-inside
orphans
widows 

The first two are used to control whether a page break should appear before or after a given element, and the latter two are common desktop publishing terms for the minimum number of lines that can appear at the end or beginning of a page. They mean the same thing in CSS2 as they do in desktop publishing.

page-break-inside (first proposed by this author, as it happens) is used to define whether or not page breaks should be placed inside a given element. For example, you might not want unordered lists to have page breaks inside them. You would then declare UL {page-break-inside: avoid;}. The rendering agent (your printer, for example) would avoid breaking unordered lists whenever possible.

There is also size, which is simply used to define whether a page should be printed in landscape or portrait mode and the length of each axis. If you plan to print your page to a professional printing system, you might want to use marks, which can apply either cross or crop marks to your page. Thus you might declare:

@page {size: 8.5in 11in; margin: 0.5in; marks: cross;}

This will set the pages to be U.S. letter-standard, 8.5 inches wide by 11 inches tall, and place cross marks in the corners of each page.

In addition, there are the new pseudo-classes :left , :right, and :first, all of which are applied only to the @page rule. Thus, you could set different margins for left and right pages in double-sided printing:

@page:left {margin-left: 0.75in; margin-right: 1in;}
@page:right{margin-left: 1in; margin-right: 0.75in;} 

The :first selector applies only to the first page of a document, so that you could give it a larger top margin or a bigger font size:

@page:first {margin-top: 2in; font-size: 150%;}

10.8.2. The Spoken Word

To round things out, we'll cover some of the properties in the area of aural style sheets. These are properties that help define how a speaking browser will actually speak the page. This may not be important to many people, but for the visually impaired, these properties are a necessity.

First off, there is voice-family, which is much the same as

P {font-size: 12px; line-height: 1.5;}
SMALL {font-size: 66%;}
BIG {font-size: 200%;}
<P>This paragraph has a line-height of 1.5 times its font-size. In addition,
any elements within it <SMALL>such as this small element</SMALL> also have
line-heights 1.5 time their font-size... and that includes <BIG>this big
element right here</BIG>. By using a scaling factor, line-heights scale
to match the font-size of any element.</P>
Figure 8-64

Figure 8-64. Using a scaling factor for line-height

font-family in its structure: the author can define both a specific voice and a generic voice family. There are several properties controlling the speed at which the page is read (speech-rate), as well as properties for the pitch
, pitch-range, stress, richness, and volume of a given voice. There are also properties that let you control how acronyms, punctuation, dates, numerals, and time are spoken. There are ways to specify audio cues, which can be played before, during, or after a given element (such as a hyperlink), ways to insert pauses before or after elements, and even the ability to control the apparent position in space from which a sound comes via the properties azimuth and elevation. With these last two properties, you could define a style sheet where the text is read by a voice "in front of" the user, whereas background music comes from "behind" and audio cues come from "above" the user!



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by side under identical lighting conditions, the background colorwould look different on each machine. This also crops up in graphicscreated for the Web, in that graphics created on Windows machinestend to appear darker to Macintosh users, whereas images created on aMacintosh look lighter for Windows users.

The situationdegrades even further when colors are printed, since factors asdiverse as the stock and color of the paper used, and even thetemperature of the printing mechanism, can affect how well colors arereproduced on paper.

In effect, this is yet anotherarea where you must remember that total control over document the chapter are not the fault of CSS but are more fundamental issues that you'll encounter no matter what you try to do with a computer. So, once you've finished this chapter, you will have a grasp not only of how CSS units work, but perhaps also of a few basic issues that you previously were unaware of.

Above all, though, regardless of how bleak things may seem, keep going! Your perseverance will be rewarded.

must be underlined and use a color similar to the standard navigation buttons found at the top of every page, which are gray text against a dark green background -- the same dark green you are to use for unvisited hyperlinks and the left edge of the browser window. All headings, including document titles, are to use a sans serif font. The rest is left to our discretion.

A lot of this is fairly straightforward. For the document BODY, we write:

space is still there because the element is still part of the document's layout. We just can't see it.

Note too that it's possible to set the descendant element of a hidden element to be visible. This would cause the element to appear wherever it normally would, despite the fact that the ancestor (and possibly the siblings) is invisible. In order to do so, you would need to explicitly declare the descendant element to be visible, since visibility is inherited. Thus: