CSS Introduction

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Table of contents

CSS Basic
CSS HOME
CSS Introduction
CSS Syntax
CSS How To
CSS Background
CSS Text
CSS Font
CSS Border
CSS Outline
CSS Margin
CSS Padding
CSS List
CSS Table
CSS Advanced
CSS Dimension
CSS Classification
CSS Positioning
CSS Pseudo-class
CSS Pseudo-element
CSS Image Gallery
CSS Image Opacity
CSS Media Types
CSS Don't
CSS Summary
CSS Examples
CSS Examples
References
CSS2 Reference
CSS2 Print
CSS2 Aural
CSS Units
CSS Colors
CSS Colorvalues
CSS Colornames
CSS Quiz
CSS Quiz
CSS Exam

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# Introduction to CSS

## What You Should Already Know

Before you continue you should have some basic understanding of the following:

- HTML / XHTML

If you want to study this subject first, find the tutorials on our Home page.

## What is CSS?

- CSS stands for Cascading Style Sheets
- Styles define how to display HTML elements
- Styles are normally stored in Style Sheets
- Styles were added to HTML 4.0 to solve a problem
- External Style Sheets can save you a lot of work
- External Style Sheets are stored in CSS files
- Multiple style definitions will cascade into one

## CSS Demo

With CSS, your HTML documents can be displayed using different output styles:

See how it works

## Styles Solve a Common Problem

HTML tags were originally designed to define the content of a document. They were supposed to say "This is a header", "This is a paragraph", "This is a table", by using tags like <h1>, <p>, <table>, and so on. The layout of the document was supposed to be taken care of by the browser, without using any formatting tags.

As the two major browsers - Netscape and Internet Explorer - continued to add new HTML tags and attributes (like the <font> tag and the color attribute) to the original HTML specification, it became more and more difficult to create Web sites where the content of HTML documents was clearly separated from the document's presentation layout.

To solve this problem, the World Wide Web Consortium (W3C) - the non profit, standard setting consortium, responsible for standardizing HTML - created STYLES in addition to HTML 4.0.

All major browsers support Cascading Style Sheets.

## Style Sheets Can Save a Lot of Work

Styles sheets define HOW HTML elements are to be displayed, just like the font tag and the color attribute in HTML 3.2. Styles are normally saved in external .css files. External style sheets enable you to change the appearance and layout of all the pages in your Web, just by editing one single CSS document!

CSS is a breakthrough in Web design because it allows developers to control the style and layout of multiple Web pages all at once. As a Web developer you can define a style for each HTML element and apply it to as many Web pages as you want. To make a global change, simply change the style, and all elements in the Web are updated automatically.

## Multiple Styles Will Cascade Into One

Style sheets allow style information to be specified in many ways. Styles can be specified inside a single HTML element, inside the <head> element of an HTML page, or in an external CSS file. Even multiple external style sheets can be referenced inside a single HTML document.

### Cascading Order

What style will be used when there is more than one style specified for an HTML element?
Generally speaking we can say that all the styles will "cascade" into a new "virtual" style sheet by the following rules, where number four has the highest priority:

1. Browser default
2. External style sheet
3. Internal style sheet (inside the <head> tag)
4. Inline style (inside an HTML element)

So, an inline style (inside an HTML element) has the highest priority, which means that it will override a style declared inside the <head> tag, in an external style sheet, or in a browser (a default value).

Note: If the external style sheet link is placed below the internal style sheet in HTML <head>, the external style sheet will override the internal style sheet.

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