What You Should Already Know
Before you continue you should have some basic understanding of the
If you want to study this subject first, find the tutorials on our
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
With CSS, your HTML documents can be displayed using different output styles:
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
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
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.
What style will be used when there is more than one style specified for an
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
- Browser default
- External style sheet
- Internal style sheet (inside the <head> tag)
- 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).
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