CSS Intro

The CSS syntax is made up of three parts: a selector, a property and a value:

selector {property: value}
body {color: black}
p {font-family: "sans serif"}

Specify more than one property, you must separate each property with a semicolon.
p
{
text-align: center;
color: black;
font-family: arial
}

You can group selectors.
h1,h2,h3,h4,h5,h6
{
color: green
}

CSS Comments

/* This is a comment */

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:

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:

hr {color: sienna}
p {margin-left: 20px}
body {background-image: url("images/back40.gif")}

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 by using the <style> tag, like this:

Inline Styles

An inline style loses many of the advantages of style sheets by mixing content with presentation. Use this method sparingly, such as when a style is to be applied to a single occurrence of an element.

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>

CSS TAGS FOR EXTERNAL CSS DOCUMENT:

body,td,th {
font-family: Arial, Helvetica, sans-serif;
font-size: 12px;
color: #FFFFFF;
background-color: #333333;
}

a:link { color: #FFCC00;
text-decoration: none;
}

a:visited { color: #999966;
text-decoration: none;
}

a:hover { color: #FFFF00;
text-decoration: none;
}

MORE SYNTAX:

The class Selector

With the class selector you can define different styles for the same type of HTML element.

Say that you would like to have two types of paragraphs in your document: one right-aligned paragraph, and one center-aligned paragraph. Here is how you can do it with styles:

p.right {text-align: right}
p.center {text-align: center}

You have to use the class attribute in your HTML document:

<p class="right">
This paragraph will be right-aligned.
</p>

<p class="center">
This paragraph will be center-aligned.
</p>

Note: Only one class attribute can be specified per HTML element! The example below is wrong:

<p class="right" class="center">
This is a paragraph.
</p>

You can also omit the tag name in the selector to define a style that will be used by all HTML elements that have a certain class. In the example below, all HTML elements with class="center" will be center-aligned:

.center {text-align: center}

In the code below both the h1 element and the p element have class="center". This means that both elements will follow the rules in the ".center" selector:

<h1 class="center">
This heading will be center-aligned
</h1>

<p class="center">
This paragraph will also be center-aligned.
</p>

Remark Do NOT start a class name with a number! It will not work in Mozilla/Firefox.

The id Selector

You can also define styles for HTML elements with the id selector. The id selector is defined as a #.

The style rule below will match the element that has an id attribute with a value of "green":

#green {color: green}

The style rule below will match the p element that has an id with a value of "para1":

p#para1
{
text-align: center;
color: red
}

Remark Do NOT start an ID name with a number! It will not work in Mozilla/Firefox.

CLASS vs. ID tags -
* ID = A person's Identification (ID) is unique to one person.
* Class = There are many people in a class.
Use IDs when there is only one occurence per page. Use classes when there are one or more occurences per page.