Cascading Style Sheets

CSS
Cascading Style Sheets

What is CSS?
 CSS stands for Cascading Style Sheets
 CSS is a language that describes the style of an HTML

document.
 CSS describes how HTML elements should be displayed.

Why Use CSS?
 CSS is used to define styles for your web pages, including
;
 Design
 layout and
 variations in display for different devices and screen
sizes.
CSS Saves a Lot of Work!
 The style definitions are normally saved in external .css
files.
 With an external stylesheet file, you can change the look

of an entire website by changing just one file!
CSS Syntax
 A CSS rule-set consists of a selector and a declaration block:
 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 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.
CSS Selectors
The element Selector:
 The element selector selects elements based on the

element name.
 Ex:
 You can select all <p> elements on a page like this (here, all <p> elements will be
center-aligned, with a red text color):
p {
text-align: center;
color: red;
}
CSS Selectors
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.
CSS Selectors
The id Selector:
 Example
 The style rule below will be applied to the
HTML element with id="para1":
#para1 {
text-align: center;
color: red;
}
 Note: An id name cannot start with a number!
CSS Selectors
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.
CSS Selectors
 Example
 In this example all HTML elements with
class="center" will be red and center-aligned:
.center {
text-align: center;
color: red;
}
CSS Selectors
 Example
 In this example only <p> elements with
class="center" will be center-aligned:
p.center {
text-align: center;
color: red;
}
 Note: A class name cannot start with a number!
CSS Selectors
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;
}
CSS Selectors
Grouping Selectors:
 It will be better to group the selectors, to minimize the code.
 To group selectors, separate each selector with a comma.

 Example
 In this example we have grouped the selectors from
the previous code:
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.

CSS Comments
 Example
 A CSS comment starts with /* and ends with */.
Comments can also span multiple lines:
p {
color: red;
/* This is a single-line comment */
text-align: center;
}
/* This is
a multi-line
comment */
Three Ways to Insert CSS
 There are three ways of inserting a style sheet:
1. External style sheet
2. Internal style sheet
3. Inline style
External Style Sheet
 With an external style sheet, you can change the look of
an entire website by changing just one file!
 Each page must include a reference to the external style

sheet file inside the <link> element.
 Example
 External styles are defined within the <link>
element, inside the <head> section of an
HTML page:
<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. The
style sheet file must be saved with a .css extension.
 "mystyle.css“
 body {
background-color: lightblue;
}
h1 {
color: navy;
margin-left: 20px;
}
Internal Style Sheet
 An internal style sheet may be used if one single page has
a unique style.
Internal Style Sheet
 Example
 Internal styles are defined within the <style> element,
inside the <head> section of an HTML page:
 <head>
<style>
body {
background-color: linen;
}
h1 {
color: maroon;
margin-left: 40px;
}
</style>
</head>
Inline Styles
 An inline style may be used to apply a unique style for a
single element.
 To use inline styles, add the style attribute to the relevant

element. The style attribute can contain any CSS property.
Inline Styles
 Example
 Inline styles are defined within the "style"
attribute of the relevant element:
 <h1 style="color:blue;margin-
left:30px;">This is a heading</h1>

Cascading Style Sheets

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CSS

Cascading Style Sheets

 CSS is a language that describes the style of an HTML

 CSS describes how HTML elements should be displayed.

 With an external stylesheet file, you can change the look

 The selector points to the HTML element you want to style.

 The element selector selects elements based on the

 The id of an element should be unique within a page, so the id

 To select an element with a specific id, write a hash (#)

 To select elements with a specific class, write a period (.)

 To group selectors, separate each selector with a comma.

 Comments are ignored by browsers.

 Each page must include a reference to the external style

 To use inline styles, add the style attribute to the relevant

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