CSS Overview

CSS Overview
Cascading Style Sheets

Svetlin Nakov
Manager Technical Training
http://nakov.com
Telerik Web Design Course
html5course.telerik.com

Table of Contents
 What is CSS?
 Styling with Cascading Stylesheets (CSS)
 Selectors and style definitions
 Linking HTML and CSS
 Font and text styles
 Backgrounds
 Colors and images

2

CSS: A New Philosophy
 Separate content from presentation!

Content Presentation
(HTML document) (CSS Document)

Title
Lorem ipsum dolor sit amet,
Bold
consectetuer adipiscing elit.
Suspendisse at pede ut purus Italics
malesuada dictum. Donec vitae
neque non magna aliquam
dictum. Indent
• Vestibulum et odio et ipsum
• accumsan accumsan. Morbi at
• arcu vel elit ultricies porta. Proin
tortor purus, luctus non, aliquam
nec, interdum vel, mi. Sed nec
quam nec odio lacinia molestie.
Praesent augue tortor, convallis
eget, euismod nonummy, lacinia
ut, risus.

3

The Resulting Page
Title
Lorem ipsum dolor sit amet,
consectetuer adipiscing elit.
Suspendisse at pede ut purus
malesuada dictum. Donec vitae neque
non magna aliquam dictum.
• Vestibulum et odio et ipsum
• accumsan accumsan. Morbi at
• arcu vel elit ultricies porta. Proin
Tortor purus, luctus non, aliquam nec,
interdum vel, mi. Sed nec quam nec
odio lacinia molestie. Praesent augue
tortor, convallis eget, euismod
nonummy, lacinia ut, risus.

4

CSS Intro
Styling with Cascading Stylesheets

CSS Introduction
 Cascading Style Sheets (CSS)
 Used to describe the presentation of documents
 Define sizes, spacing, fonts, colors, layout, etc.
 Improve content accessibility
 Improve flexibility
 Designed to separate presentation from content
 Due to CSS, all HTML presentation tags and
attributes are deprecated, e.g. font, center, etc.

6

CSS Introduction (2)
 CSS can be applied to any XML document

 Not just to HTML / XHTML
 CSS can specify different styles for different

media
 On-screen
 In print
 Handheld, projection, etc.
 … even by voice or Braille-based reader

7

Why “Cascading”?
 Priority scheme determining which style rules

apply to element
 Cascade priorities or specificity (weight) are
calculated and assigned to the rules
 Child elements in the HTML DOM tree inherit
styles from their parent
 Can override them
 Control via !important rule

8

Why “Cascading”? (2)

9

Stile Inheritance
 Some CSS styles are inherited and some not

 Text-related and list-related properties are
inherited - color, font-size, font-family,
line-height, text-align, list-style, etc.
 Box-related and positioning styles are not
inherited - width, height, border, margin,
padding, position, float, etc
 <a> elements do not inherit color and text-
decoration

10

Style Sheets Syntax
 Stylesheets consist of rules, selectors,
declarations, properties and values

http://css.maxdesign.com.au/
 Selectors are separated by commas
 Declarations are separated by semicolons
 Properties and values are separated by colons
h1,h2,h3 { color: green; font-weight: bold; }
11

Selectors
 Selectors determine which element the rule

applies to:
 All elements of specific type (tag)
 Those that match a specific attribute (id, class)
 Elements may be matched depending on how
they are nested in the document tree (HTML)
 Examples:

.header a { color: green }

#menu>li { padding-top: 8px }
12

Selectors (2)
 Three primary kinds of selectors:
 By tag (type selector):
h1 { font-family: verdana,sans-serif; }
 By element id:
#element_id { color: #ff0000; }
 By element class name (only for HTML):
.myClass {border: 1px solid red}
 Selectors can be combined with commas:
h1, .link, #top-link {font-weight: bold}

This will match <h1> tags, elements with class
link, and the element with id top-link
13

Selectors (3)
 Pseudo-classes define state

 :hover, :visited, :active , :lang
 Pseudo-elements define element "parts" or are

used to generate content
 :first-line , :before, :after

a:hover { color: red; }
p:first-line { text-transform: uppercase; }
.title:before { content: "»"; }
.title:after { content: "«"; }

14

Selectors (4)
 Match relative to element placement:
p a {text-decoration: underline}

This will match all <a> tags that are inside of <p>
 * – universal selector (avoid or use with care!):
p * {color: black}

This will match all descendants of <p> element
 + selector – used to match “next sibling”:
img + .link {float:right}

This will match all siblings with class name link
that appear immediately after <img> tag 15

Selectors (5)
 > selector – matches direct child nodes:
p > .error {font-size: 8px}
This will match all elements with class error, direct
children of <p> tag
 [ ] – matches tag attributes by regular expression:

img[alt~=logo] {border: none}
This will match all <img> tags with alt attribute
containing the word logo
 .class1.class2 (no space) - matches elements
with both (all) classes applied at the same time

16

Values in the CSS Rules
 Colors are set in RGB format (decimal or hex):
 Example: #a0a6aa = rgb(160, 166, 170)
 Predefined color aliases exist: black, blue, etc.
 Numeric values are specified in:
 Pixels, ems, e.g. 12px , 1.4em
 Points, inches, centimeters, millimeters
 E.g. 10pt , 1in, 1cm, 1mm
 Percentages, e.g. 50%
 Percentage of what?...
 Zero can be used with no unit: border: 0;
17

Default Browser Styles
 Browsers have predefined CSS styles

 Used when there is no CSS information or any
other style information in the document
 Caution: default styles differ in browsers

 E.g. margins, paddings and font sizes differ
most often
 Usually developers reset them
* { margin: 0; padding: 0; }

body, h1, p, ul, li { margin: 0; padding: 0; }

18

Linking HTML and CSS
 HTML (content) and CSS (presentation) can be
linked in three ways:
 Inline: the CSS rules in the style attribute
 No selectors are needed
 Embedded: in the <head> in a <style> tag
 External: CSS rules in separate file (best)
 Usually a file with .css extension
 Linked via <link rel="stylesheet" href="
…"> tag
 Via @import directive in embedded CSS block
19

Linking HTML and CSS (2)

 Using external files is highly recommended

 Simplifies the HTML document
 Improves page load speed as the CSS file is
cached

20

Inline Styles: Example
inline-styles.html
<!DOCTYPE html>
<html lang="en">
<head>
<title>Inline Styles</title>
</head>
<body>
<p>Here is some text</p>

<p style="font-size: 20pt">Here is some
more text</p>
<p style="font-size: 20pt;color:
#0000FF" >Even more text</p>
</body>
</html>

21

Inline Styles: Example
inline-styles.html
<!DOCTYPE html>
<html lang="en">
<head>
<title>Inline Styles</title>
</head>
<body>
<p>Here is some text</p>

<p style="font-size: 20pt">Here is some
more text</p>
<p style="font-size: 20pt;color:
#0000FF" >Even more text</p>
</body>
</html>

22

CSS Cascade (Precedence)
 There are browser, user and author stylesheets

with "normal" and "important" declarations
 Browser styles (least priority)
 Normal user styles
 Normal author styles (external, in head, inline)
 Important author styles
 Important user styles (max priority)
a { color: red !important ; }

http://www.slideshare.net/maxdesign/css-cascade-1658158
23

CSS Specificity
 CSS specificity is used to determine the

precedence of CSS style declarations with the
same origin. Selectors are what matters
 Simple calculation: #id = 100, .class = 10,
:pseudo = 10, [attr] = 10, tag = 1, * = 0
 Same number of points? Order matters!
 See also:
 http://www.smashingmagazine.com/2007/07/27/css-specificity-things-you-

 http://css.maxdesign.com.au/selectutorial/advanced_conflict.htm

24

CSS Rules Precedence
Live Demo
precedence.html

Embedded Styles
 Embedded in the HTML in the <style> tag:
<style type="text/css">

 The <style> tag is placed in the <head>
section of the document
 type attribute specifies the MIME type
 MIME describes the format of the content
 Other MIME types include text/html,
image/gif, text/javascript …
 Used for document-specific styles

26

Embedded Styles: Example

embedded-stylesheets.html
<!DOCTYPE html>
<html>
<head>
<title>Style Sheets</title>
em {background-color:#8000FF; color:white}
h1 {font-family:Arial, sans-serif}
p {font-size:18pt}
.blue {color:blue}
</style>
<head>

27

Embedded Styles: Example (2)
…
<body>
<header>
<h1 class="blue">A Heading</h1>
</header>
<article>
<p>Here is some text. Here is some text.
Here is some text. Here is some text. Here
is some text.</p>
<h1>Another Heading</h1>
<p class="blue">Here is some more text.
Here is some more text.</p>
<p class="blue">Here is some <em>more</em>
text. Here is some more text.</p>
</article>
</body>
</html>
28

Embedded Styles: Example (3)
…
<body>
<header>
<h1 class="blue">A Heading</h1>
</header>
<article>
<p>Here is some text. Here is some text.
Here is some text. Here is some text. Here
is some text.</p>
<h1>Another Heading</h1>
<p class="blue">Here is some more text.
Here is some more text.</p>
<p class="blue">Here is some <em>more</em>
text. Here is some more text.</p>
</article>
</body>
</html>
29

External CSS Styles
 External linking
 Separate pages can all use a shared style sheet
 Only modify a single file to change the styles across
your entire Web site (see http://www.csszengarden.com/)
 link tag (with a rel attribute)
 Specifies a relationship between current document
and another document
<link rel="stylesheet" type="text/css"
href="styles.css">
 link elements should be in the <head>
30

External CSS Styles (2)
@import
 Another way to link external CSS files
 Example:
@import url("styles.css");
/* same as */
@import "styles.css";
</style>

 Ancient browsers do not recognize @import

 Use @import in an external CSS file to
workaround the IE 32 CSS file limit
31

External Styles: Example
styles.css
/* CSS Document */

a { text-decoration: none }

a:hover { text-decoration: underline;
color: red;
background-color: #CCFFCC }

li em { color: red;
font-weight: bold }

ul { margin-left: 2cm }

ul ul { text-decoration: underline;
margin-left: .5cm }

32

External Styles: Example (2)
external-styles.html
<!DOCTYPE html>
<html>
<head>
<title>Importing style sheets</title>
<link type="text/css" rel="stylesheet"
href="styles.css" />
</head>
<body>
<h1>Shopping list for <em>Monday</em>:</h1>
<li>Milk</li>
…

33

…
<li>Bread
<ul>
<li>White bread</li>
<li>Rye bread</li>
<li>Whole wheat bread</li>
</ul>
</li>
<li>Rice</li>
<li>Potatoes</li>
<li>Pizza <em>with mushrooms</em></li>
</ul>
<a href="http://food.com" title="grocery
store">Go to the Grocery store</a>
</body>
</html>
34

…
<li>Bread
<ul>
<li>White bread</li>
<li>Rye bread</li>
<li>Whole wheat bread</li>
</ul>
</li>
<li>Rice</li>
<li>Potatoes</li>
<li>Pizza <em>with mushrooms</em></li>
</ul>
<a href="http://food.com" title="grocery
store">Go to the Grocery store</a>
</body>
</html>
35

Text-related CSS Properties
 color – specifies the color of the text
 font-size – size of font: xx-small, x-small,
small, medium, large, x-large, xx-large,
smaller, larger or numeric value
 font-family – comma separated font names
 Example: verdana, sans-serif, etc.
 The browser loads the first one that is available
 There should always be at least one generic font
 font-weight can be normal, bold, bolder,
lighter or a number in range [100 … 900]
37

CSS Rules for Fonts (2)
 font-style – styles the font

 Values: normal, italic, oblique
 text-decoration – decorates the text

 Values: none, underline, line-trough,
overline, blink
 text-align – defines the alignment of text or

other content
 Values: left, right, center, justify

38

Shorthand Font Property
 font

 Shorthand rule for setting multiple font
properties at the same time
font:italic normal bold 12px/16px verdana
is equal to writing this:
font-style: italic;
font-variant: normal;
font-weight: bold;
font-size: 12px;
line-height: 16px;
font-family: verdana;
39

Fonts
Live Demo
font-rules.html

Backgrounds
 background-image

 URL of image to be used as background, e.g.:
background-image:url("back.gif");

 background-color

 Using color and image and the same time
 background-repeat

 repeat-x, repeat-y, repeat, no-repeat
 background-attachment

 fixed / scroll 42

Backgrounds (2)
 background-position: specifies vertical and

horizontal position of the background image
 Vertical position: top, center, bottom
 Horizontal position: left, center, right
 Both can be specified in percentage or other
numerical values
 Examples:
background-position: top left;

background-position: -5px 50%;
43

Background Shorthand Property
 background: shorthand rule for setting
background properties at the same time:
background: #FFF0C0 url("back.gif") no-repeat
fixed top;

is equal to writing:
background-color: #FFF0C0;
background-image: url("back.gif");
background-repeat: no-repeat;
background-attachment: fixed;
background-position: top;

 Some browsers will not apply BOTH color and
image for background if using shorthand rule 44

Background-image or <img>?
 Background images allow you to save many

image tags from the HTML
 Leads to less code
 More content-oriented approach
 All images that are not part of the page

content (and are used only for "beautification")
should be moved to the CSS

45

Background Styles
Live Demo
background-rules.html

CSS Reference
 A list of all CSS 2.1 properties is available at

http://www.w3.org/TR/CSS2/propidx.html

47

CSS Overview

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Homework
1. Create the following page section using HTML and
external CSS (no inline styles). Use a table or a
definition list (in this case the layout will be
different).

49

Homework (2)
1. Create the following Web page using external CSS
styles.

50

Homework (3)
1. Implement the following
using CSS styles

51

Homework (4)
1. Implement the following using tables and CSS

52

CSS Overview

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