HTML and CSS Reference
Understanding CSS and the Modern
IN THIS CHAPTER, you'll learn what the modern web is and why CSS is so important to it.
What Is the Modern Web?
Most importantly, the web today is what it has always been—accessible information. Unlike the early days of the web,
though—when it was just a collection of text files—the modern web has grown to support many differing media
formats and now, more than ever, many differing ways to access information.
No longer do you just sit at a desktop computer to “log on.” Nowadays, you sit on a beach reading the news on a tab-
let device, you go to a coffee shop with laptop in hand to chat with friends in different countries, and you try to refrain
from laughing at pictures of cats playing keyboards while viewing a smart phone on a train journey. The information
on the web is practically infinite (more content is created than you could ever consume), and the way in which you ac-
cess that information continues to grow.
The modern web is an exciting media to be a part of. It is continuously growing and so too are the technologies behind
What Is CSS?
Cascading Style Sheets (CSS) is a simple language defining styles that can be applied to HTML. Where HTML de-
scribes the structure of a web page, CSS describes its presentation.
An international community called the World Wide Web Consortium (W3C) writes and maintains the CSS specifica-
tions that define and standardize the way in which people should write the CSS language and browser vendors (the
people who make web browsers) should implement it. Because the CSS specification has grown since its introduction
in 1996, the latest version, CSS3, has been broken up into modules so that each defines a part of CSS, making the
overall specification easier to maintain.
You can find the CSS specifications at www.w3.org/Style/CSS/ . Because these specifications are very much
technical and in depth, you may find them off-putting. I know I do! Although they are useful to refer to from time to
time, by no means do you need to read them. CSS3 Foundations takes a much more simple and friendly approach to
your understanding of CSS3.
Before you take a closer look at what CSS can offer, you should first understand the current state of CSS. You may
have noticed I referred to both CSS and CSS3. What's the difference?
CSS refers to all three levels of the specification: CSS Level 1 (CSS1), CSS Level 2 (CSS2), and CSS Level 3
(CSS3). Each level of CSS builds on its predecessor. CSS2 had a shaky start and many issues came to light, leading to
a revision of this specification and the release of CSS2.1. So, CSS3 contains aspects of its predecessor CSS2.1, and
CSS2.1 contains aspects of CSS2 and CSS1.