Overview & Syntax

What is CSS?

CSS stands for Cascading Style Sheets
CSS describes how HTML elements are to be displayed on screen, paper, or in other media
CSS saves a lot of work. It can control the layout of multiple web pages all at once
External stylesheets are stored in CSS files
CSS is a language that describes the style of an HTML document.
CSS describes how HTML elements should be displayed.

CSS Example

body {
    background-color: lightblue;
}

h1 {
    color: white;
    text-align: center;
}

p {
    font-family: verdana;
    font-size: 20px;
}

CSS Syntax and Selectors

CSS Syntax

A CSS rule-set consists of a selector and a declaration block:
h1 {color:blue;font-size:12px;}
Here h1 is the selector
color and font-size are properties
blue and 12px are values given to the properties
the combination of Property:Value is called Declaration.

The selector points to the HTML element you want to style.
The declaration block contains one or more declarations separated by semicolons.
declaration includes a CSS property name and a value, separated by a colon.
A CSS declaration always ends with a semicolon, and declaration blocks are surrounded by curly braces.

CSS Selectors

CSS selectors are used to "find" (or select) HTML elements based on their element name, id, class, attribute, and more.

The element Selector

The element selector selects elements based on the element name. You can select all elements on a page like this (in this case, all elements will be center-aligned, with a red text color):

Example

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

The id Selector

The id selector uses the id attribute of an HTML element to select a specific element. The id of an element should be unique within a page, so the id selector is used to select one unique element! To select an element with a specific id, write a hash (#) character, followed by the id of the element. The style rule below will be applied to the HTML element with id="para1":

Example

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

The class Selector

The class selector selects elements with a specific class attribute. To select elements with a specific class, write a period (.) character, followed by the name of the class. In the example below, all HTML elements with class="center" will be red and center-aligned:

Example

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

You can also specify that only specific HTML elements should be affected by a class. In the example below, only elements with class="center" will be center-aligned:

Example

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

HTML elements can also refer to more than one class. In the example below, the element will be styled according to class="center" and to class="large":

Example

This paragraph refers to two classes.
Note: A class name cannot start with a number!

Grouping Selectors

If you have elements with the same style definitions, like this:


h1 {
    text-align: center;
    color: red;
}

h2 {
    text-align: center;
    color: red;
}

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

It will be better to group the selectors, to minimize the code. To group selectors, separate each selector with a comma. In the example below we have grouped the selectors from the code above:

Example

h1, h2, p {
    text-align: center;
    color: red;
}

CSS Comments

Comments are used to explain the code, and may help 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:

Example

p {
    color: red;
    /* This is a single-line comment */
    text-align: center;
}

/* This is
a multi-line
comment */

« Previous Next »