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2.12 Style Sheets and JavaScript
Browsers also have support for two
powerful innovations to HTML: style sheets and JavaScript. Like their
desktop-publishing cousins, style sheets let you control how your web
pages look text font styles and sizes, colors, backgrounds,
alignments, and so on. More importantly, style sheets give you a way
to impose display characteristics uniformly over the entire document
and over an entire collection of documents.
JavaScript is a programming language
with functions and commands that let you control how the browser
behaves for the user. Now, this is not a JavaScript programming book,
but we do cover the language in fair detail in later chapters to show
you how to embed JavaScript programs into your documents and achieve
some very powerful and fun effects.
The W3C the putative standards organization prefers that
you use the Cascading Style Sheets (CSS) model for
HTML/XHTML document design. Since Version 4, both Netscape and
Internet Explorer support CSS and
JavaScript. Netscape 4 alone also supports a JavaScript-based Style Sheet ( JSS)
model, which we describe in Chapter 12, but we do
not recommend that you use it. CSS is the universally approved,
universally supported way to control how your documents might (not
will) usually be displayed on users' browsers.
To illustrate CSS, here's a way to make all the
top-level (H1) header text in your HTML document appear in the color
red:
<html>
<head>
<title>CSS Example</title>
<!-- Hide CSS properties within comments so old browsers
don't choke on or display the unfamiliar contents. -->
<style type="text/CSS">
<!--
H1 {color: red}
-->
</style>
</head>
<body>
<H1>I'll be red if your browser supports CSS</H1>
Something in between.
<H1>I should be red, too!</H1>
</body>
</html>
Of course, you can't see red in this black and white
book, so we won't show the result in a figure.
Believe us, or prove it to yourself by typing in and loading the
example in your browser: the <H1>-enclosed
text appears red on a color screen.
JavaScript is an object-based language. It views your document and
the browser that displays your documents as a collection of parts
("objects") that have certain
properties that you may change or compute. This is some very powerful
stuff, but not something that most authors will want to handle.
Rather, most of us probably will snatch the quick and easy, yet
powerful JavaScript programs that proliferate across the Web and
embed them in our own documents. We will tell you how in
Chapter 12.
