CSS: An Overview

In our CSS tutorial you will learn how to use CSS to control the style and layout of multiple Web pages all at once. Before you continue you should have a basic understanding of HTML. If you’re ready, Let’s get started!


What is CSS?

  • CSS stands for Cascading Style Sheets
  • CSS defines how HTML elements are to be displayed
  • Styles were added to HTML 4.0 to solve a problem
  • CSS saves a lot of work
  • External Style Sheets are stored in CSS files

CSS Solved a Big Problem

HTML was NEVER intended to contain tags for formatting a document.

HTML was intended to define the content of a document, like:

<h1>This is a heading</h1>

<p>This is a paragraph.</p>

When tags like <font>, and color attributes were added to the HTML 3.2 specification, it started a nightmare for web developers. Development of large web sites, where fonts and color information were added to every single page, became a long and expensive process.

To solve this problem, the World Wide Web Consortium (W3C) created CSS.

In HTML 4.0, all formatting could (and should!) be removed from the HTML document, and stored in a separate CSS file.

CSS Saves a Lot of Work!

The style definitions are normally saved in external .css files.

With an external style sheet file, you can change the look of an entire Web site by changing just one file!

II-CSS Syntax

A CSS rule set consists of a selector and a declaration block:

CSS selector

The selector points to the HTML element you want to style.

The declaration block contains one or more declarations separated by semicolons.

Each declaration includes a property name and a value, separated by a colon.

CSS Example

A CSS declaration always ends with a semicolon, and declaration groups are surrounded by curly braces:

 p {color:red;text-align:center;}

To make the CSS code more readable, you can put one declaration on each line.


CSS Comments

Comments are used to explain your code, and may help you when you edit the source code at a later date. Comments are ignored by browsers.

A CSS comment starts with /* and ends with */. Comments can also span multiple lines:


       color: red;
       /* This is a single-line comment */
      text-align: center;
 /* This is
 a multi-line
 comment */
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