Datasheet

standards body, I may discuss these features anyway if at least one browser maker has implemented the
feature in question. I preface any such discussion with the warning that these features are still under
development and could be subject to change.
This book discusses the portions of CSS available in browsers at the time of this writing—that includes
most of CSS 2 and CSS 2.1, and a little of CSS 3. Some portions of CSS 2.1 contradict CSS 2 and are not
yet implemented in any browser. Where appropriate throughout the book and before introducing a new
CSS feature, I reference the W3C specification in which that CSS feature is documented by including the
phrase Documented in CSS followed by the version number. Later in this chapter, I discuss the browsers
that you need to test and build CSS-enabled web documents.
You can find the W3C website at
www.w3.org. Go there to find documents that browser makers refer to
when they are looking to implement languages such as CSS into a browser or other software. Be advised,
these specifications lean heavily toward the technical side. They aren’t intended as documentation for
people who use CSS; rather, they are aimed at those who write programs that interpret CSS. Despite the
heavily technical nature of the W3C specification documents, many web developers refer to the W3C
documents as end-user documentation anyway, since it is the most complete resource.
Now that you know a little about who is responsible for planning and outlining the development of CSS,
the next section describes how a web document makes its way into your browser.
How the Internet Works
As you probably already know, the Internet is a complex network of computers. Most of what goes on
behind the scenes is of little interest to the person developing content for a website, but it is important to
understand some of the fundamentals of what happens when you type an Internet address into your
browser. Figure 1-1 shows a simple diagram of this process.
At the top of the diagram in Figure 1-1, you see a computer labeled server-side and a computer labeled
client-side. The diagram is by no means an exhaustive or complete picture of what happens when you
type in an Internet address, but it serves the purpose of illustrating the portions of the process that the
aspiring web designer needs to understand. The server-side computer houses the documents and data
of the website and is generally always running so that the website’s visitors can access the website at any
time of day. The client-side computer is, of course, your own computer.
The server-side computer contains HTTP server software that handles all the incoming requests for web
pages. When you type an Internet address into a browser, the browser sends out a request that travels
through a long network of computers that act as relays for that request until the address of the remote
(server-side) computer is found. After the request reaches the HTTP server, the HTTP server sees what it
is you are trying to find, searches for the page on the server’s hard drive, and responds to the request
you’ve made, sending the web page that you expect. That response travels back through another long
chain of computers until your computer is found. Your browser then opens the response and reads what
the HTTP server has sent back to it. If that server has sent an HTML document or another type of docu-
ment that your browser can interpret, it reads the source code of that document and processes it into a
displayable web page.
5
Chapter 1: Introducing Cascading Style Sheets
05_096970 ch01.qxp 4/20/07 11:27 PM Page 5