Three Ways to Insert CSS
There are three ways of inserting a style sheet:

External style sheet
Internal style sheet
Inline style
External Style Sheet
An external style sheet is ideal when the style is applied to many pages. With an external style sheet, you can change the look of an entire Web site by changing one file. Each page must link to the style sheet using the tag. The tag goes inside the head section:

An external style sheet can be written in any text editor. The file should not contain any html tags. Your style sheet should be saved with a .css extension. An example of a style sheet file is shown below:
[css]
hr {color:sienna;}
p {margin-left:20px;}
body {background-image:url("images/background.gif");}
[/css]
Note Do not add a space between the property value and the unit (such as margin-left:20 px). The correct way is: margin-left:20px

Internal Style Sheet
An internal style sheet should be used when a single document has a unique style. You define internal styles in the head section of an HTML page, by using the

Inline Styles
An inline style loses many of the advantages of style sheets by mixing content with presentation. Use this method sparingly!

To use inline styles you use the style attribute in the relevant tag. The style attribute can contain any CSS property. The example shows how to change the color and the left margin of a paragraph:

This is a paragraph.

Multiple Style Sheets
If some properties have been set for the same selector in different style sheets, the values will be inherited from the more specific style sheet.

For example, an external style sheet has these properties for the h3 selector:
[css]
h3{
color:red;
text-align:left;
font-size:8pt;
}
[/css]
And an internal style sheet has these properties for the h3 selector:
[css]
h3{
text-align:right;
font-size:20pt;
}
[/css]
If the page with the internal style sheet also links to the external style sheet the properties for h3 will be:
[css]
color:red;
text-align:right;
font-size:20pt;
[/css]
The color is inherited from the external style sheet and the text-alignment and the font-size is replaced by the internal style sheet.

Multiple Styles Will Cascade into One
Styles can be specified:

inside an HTML element
inside the head section of an HTML page
in an external CSS file
Tip: 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:

Browser default
External style sheet
Internal style sheet (in the head section)
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 defined inside thetag, or in an external style sheet, or in a browser (a default value).

Et harum quidem rerum facilis est et expedita distinctio.

CSS selectors are used to « find » (or select) HTML elements based on their id, classes, types, attributes, values of attributes and much more.

The element Selector
The element selector selects elements based on the element name.

You can select all

elements on a page like this: (all

elements will be center-aligned, with a red text color)

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

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 brackets:

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

To make the CSS more readable, you can put one declaration on each line, like this:

Example

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

Try it yourself »

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:

HTML / XHTML
If you want to study these subjects 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 were added to HTML 4.0 to solve a problem
External Style Sheets can save a lot of work
External Style Sheets are stored in CSS files
CSS Demo
An HTML document can be displayed with different styles: See how it works

Styles 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:

This is a heading

This is a paragraph.

When tags like , 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.

Styles are normally saved in external .css files. External style sheets enable you to change the appearance and layout of all the pages in a Web site, just by editing one single file!