Learn CSS
Css
<html>
<head>
<style>
body {background-color:pink;}
h1 {font-size:36pt;}
h2 {color:blue;}
p
{margin-left:50px;}
</style>
</head>
<body>
<h1>This header is 36 pt</h1>
<h2>This header is blue</h2>
<p>This paragraph has a left margin of 50
pixels</p>
</body>
</html>
<html>
<head>
<style>
body {background-color:tan;}
h1
{color:maroon;font-size:20pt;}
hr {color:navy;}
p
{font-size:11pt;margin-left:15px;}
a:link
{color:green;}
a:visited {color:yellow;}
a:hover
{color:black;}
a:active
{color:blue;}
</style>
</head>
<body>
<h1>This is a header 1</h1>
<hr>
<p>You can see that the style
sheet formats the text</p>
<p><a href="http://www.w3schools.com"
target="_blank">This is a link</a></p>
</body>
</html>
What
You Should Already Know
Before you continue you should have
a basic understanding of the following:
- HTML / XHTML
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
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:
<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 be
removed from the HTML document, and stored in a separate CSS file.
All browsers support CSS today.
CSS
Saves a Lot of Work!
CSS defines HOW HTML elements are to
be displayed.
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!
body
{
background-color:#d0e4fe;
}
h1
{
color:orange;
text-align:center;
}
p
{
font-family:"Times New Roman";
font-size:20px;
}
{
background-color:#d0e4fe;
}
h1
{
color:orange;
text-align:center;
}
p
{
font-family:"Times New Roman";
font-size:20px;
}
CSS
Syntax
A CSS rule has two main parts: a
selector, and one or more declarations:
The selector is normally the HTML
element you want to style.
Each declaration consists of a
property and a value.
The property is the style attribute
you want to change. Each property has a value.
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;
}
{
color:red;
text-align:center;
}
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 begins with
"/*", and ends with "*/", like this:
/*This is a comment*/
p
{
text-align:center;
/*This is another comment*/
color:black;
font-family:arial;
}
p
{
text-align:center;
/*This is another comment*/
color:black;
font-family:arial;
}
<!DOCTYPE html>
<html>
<head>
<style>
p
{
color:red;
text-align:center;
}
</style>
</head>
<body>
<p>Hello World!</p>
<p>This paragraph is styled with CSS.</p>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<style>
#para1
{
text-align:center;
color:red;
}
</style>
</head>
<body>
<p id="para1">Hello World!</p>
<p>This paragraph is not affected by the
style.</p>
</body>
</html>
The
id and class Selectors
In addition to setting a style for a
HTML element, CSS allows you to specify your own selectors called
"id" and "class".
The
id Selector
The id selector is used to specify a
style for a single, unique element.
The id selector uses the id
attribute of the HTML element, and is defined with a "#".
The style rule below will be applied
to the element with id="para1":
Example
#para1
{
text-align:center;
color:red;
}
{
text-align:center;
color:red;
}
Do
NOT start an ID name with a number! It will not work in Mozilla/Firefox.
The
class Selector
The class selector is used to
specify a style for a group of elements. Unlike the id selector, the class
selector is most often used on several elements.
This allows you to set a particular
style for many HTML elements with the same class.
The class selector uses the HTML
class attribute, and is defined with a "."
In the example below, all HTML
elements with class="center" will be center-aligned:
Example
.center {text-align:center;}
You can also specify that only
specific HTML elements should be affected by a class.
In the example below, all p elements
with class="center" will be center-aligned:
Example
p.center {text-align:center;}
Do
NOT start a class name with a number! This is only supported in Internet
Explorer.
<!DOCTYPE html>
<html>
<head>
<style>
.center
{
text-align:center;
}
</style>
</head>
<body>
<h1 class="center">Center-aligned
heading</h1>
<p class="center">Center-aligned
paragraph.</p>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<style>
p.center
{
text-align:center;
}
</style>
</head>
<body>
<h1 class="center">This heading will not be
affected</h1>
<p class="center">This paragraph will be
center-aligned.</p>
</body>
</html>
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 <link> tag. The <link> tag goes inside the head section:
<head>
<link rel="stylesheet" type="text/css" href="mystyle.css">
</head>
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:<link rel="stylesheet" type="text/css" href="mystyle.css">
</head>
hr {color:sienna;}
p {margin-left:20px;}
body {background-image:url("images/back40.gif");}
p {margin-left:20px;}
body {background-image:url("images/back40.gif");}
Do not add a space
between the property value and the unit (such as margin-left:20 px). The
correct way is: margin-left:20pxInternal 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 <style> tag, like this:
<head>
<style>
hr {color:sienna;}
p {margin-left:20px;}
body {background-image:url("images/back40.gif");}
</style>
</head>
<style>
hr {color:sienna;}
p {margin-left:20px;}
body {background-image:url("images/back40.gif");}
</style>
</head>
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:
<p
style="color:sienna;margin-left:20px">This is a paragraph.</p>
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:
h3
{
color:red;
text-align:left;
font-size:8pt;
}
And an internal style sheet has these properties for the h3 selector:{
color:red;
text-align:left;
font-size:8pt;
}
h3
{
text-align:right;
font-size:20pt;
}
If the page with the internal style sheet also links to the external style
sheet the properties for h3 will be:{
text-align:right;
font-size:20pt;
}
color:red;
text-align:right;
font-size:20pt;
The color is inherited from the external style sheet and the text-alignment
and the font-size is replaced by the internal style sheet.text-align:right;
font-size:20pt;
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
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)
Note: If the
link to the external style sheet is placed after the internal style sheet in
HTML <head>, the external style sheet will override the internal style
sheet!Common Declarations
HTML5
<!DOCTYPE html>
HTML 4.01
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01
Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
"http://www.w3.org/TR/html4/loose.dtd">
XHTML 1.0
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0
Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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