CSS

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Cascading Style Sheets
C S S

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What is CSS?
• A simple mechanism for controlling the style
of a Web document without compromising its
structure.
• It allows you to separate visual design
elements (layout, fonts, colors, margins, and
so on) from the contents of a Web page.
• Allows for faster downloads, streamlined site
maintenance, and global control of design
attributes across multiple pages.

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CSS vs. just HTML
• What can we do with CSS that we can’t do
with HTML?
– Control of backgrounds.
– Set font size to the exact height you want.
– Highlight words, entire paragraphs, headings
or even individual letters with background
colors.
– Overlap words and make logo-type headers
without making images.
– Precise positioning.
– Linked style sheets to control the look of a
whole website from one single location.
– And more.

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How to write CSS?
• Selector
– HTML element tags
(examples: p, h2, body, img, table)
– class and ID names
• Property (examples: color, font-size)
• Value (examples: red, 14pt)

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How to write CSS:
• The basic syntax of a CSS rule:
selector {property 1: value 1; property 2:
value 2}
Example:
p {font-size: 8pt; color: red}
Notice the { } around the rule and the : before
each value!

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Three ways to include CSS:
1. Local (Inline)
2. Global (Embedded, or Internal)
3. Linked (External)

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1. Local
• Inline style sheet.
• Placed inside tags.
• Specific to a single instance of an html
tag on a page.
• Must be used instead of <font> tags to
specify font size, color, and typeface
and to define margins, etc.
• Use to override an external or
embedded style specification.

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Local (inline)
• Example
<p style="font-size: 10pt; color: red; font-weight:
bold; font-family: Arial, Helvetica, sans-serif">
This is a local stylesheet declaration. </p>
On the browser:

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2. Global
• Embedded or internal style sheet
• Applicable to an entire document
• Styles are defined within the <style>
</style> tag, which is placed in the
header of the html file (i.e., within
<head> and </head>).

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Global (Internal)
• Example:
<html>
<head>
<title>Title</title>
<style type="text/css">

</style>
</head>
<body>
[DOCUMENT BODY GOES HERE]
</body>
</html>

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3. Linked
• External style sheet
• Styles are saved in a separate file, with
the extension .css
• This single stylesheet can be used to
define the look of multiple pages.

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Linked (External)
• Example
p {font-family: verdana, sans-
serif; font-size: 12pt; color: red}
h1 {font-family: serif; font-size:
14pt; color: green}
h2 {font-family: serif; font-size:
11pt; color: blue}
Save this text
file as
whatever.css
In TextPad,Notepad, etc.…

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Linked (External)
• Example (continued)
To apply the stylesheet “whatever.css“
to an HTML document, call it in from the
header:
<head>
<link rel="stylesheet"
href=“whatever.css" type="text/css">
</head>

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Inheritance: which style prevails
when several are present?
• Inline (local) overrides internal (global)
• Internal (global) overrides external (linked).

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Cascading
The way styles will be used when there is more than one
style specified for an HTML element:
1. Browser default
2. External Style Sheet (Linked) (in an external .css file)
3. Internal Style Sheet (Global, or embedded) (inside the <head>
tag)
4. Inline Style (Local) (inside HTML element)
• An inline style (inside an HTML element) has the highest
priority, which means that it will override every style declared
inside the <head> tag, in an external style sheet, and in the
browser (default value).

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Let’s try this now!
<h1 style=“text-align: center; font-
weight:bold; color: blue”> Styling with CSS!
</h1>
<p style="font-size: 10pt; color: red; font-
weight: bold; font-family: Arial, Helvetica,
sans-serif“ >
Write whatever you want here </p>

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Grouping properties
• Separate properties with a semi-colon
– Example:
p {text-align:center;color:red; font-
family:Arial; font-style:italic}

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Grouping selectors
• Separate selectors with a comma
– Example:
h1,h2,h3,h4,h5,h6 { color: green }
(each header will be green)
• Separate selectors with a space
– Example:
p li { color: red }
(only items within a list and a
paragraph tag will be red)

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The class Selector
• With a class selector you can define different
styles for the same type of HTML element
• Examples:
First define the class:
p.right {text-align: right; color: red; font-style: italic}
p.blue {text-align: center; color:blue}
Then use the class in your HTML code :
<p class="right"> This paragraph will be right-
aligned, italic, and red. </p>
<p class=“blue"> This paragraph will be center-
aligned and blue. </p>

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The class Selector
• You can also omit the tag name in the
selector to define a style that will be used by
all HTML elements that have this class.
• Example:
.poem {text-align: center; font-style:italic}
Any HTML element with class=“poem" will be
center-aligned and italic.

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The class Selector
• Example (continued)
Both elements below will follow the
rules in the ".poem“ class:
<h1 class=“poem"> This heading will be
center-aligned and italic </h1>
<p class=“poem"> This paragraph will also
be center-aligned and italic. </p>

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Class Example
<style>
p {font-family: sans-serif; font-size: 10pt}
h1 {font-family: serif; font-size: 30pt}
h2 {font-family: serif; font-size: 24pt}
.boldred {color: red; font-weight: bold}
.green {color: green}
.tinyblue {color: blue; font-size: 8pt}
</style>
The tags and classes can then be used in combination:
<h1 class=“boldred">This is rendered as 30-point red serif bold
text.</h1>
<p class=“boldred">This is rendered as 10-point red sans-serif bold
text.</p>

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Applying styles to portions of
a document:
• <div>
– A division tag: to “package” a block of
document into one unit. It defines a block
element.
– Causes a line break, like <br> and <p>.
• <span>
– “Wraps” a portion of text into a unit, but
doesn't cause a line break. Allows styles to
be applied to an 'elemental' region (such
as a portion of a paragraph).

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Example
<p><span class="foo">This text is rendered
as foo-style</span> and this is not. </p>
<div class="foo">
<p>The "foo" style will be applied to this text,
and to <a href="page.html">this text</a> as
well.
</div>

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List of style Selectors and
their Properties and Values:
• From WDG:
http://www.htmlhelp.com/reference/css/properties.html

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Properties - Font
• font-family
– Name, or serif, sans-serif, cursive, monospace
• font-style
– normal, italic
• font-weight
– normal, bold, 100, 200, 300, 400, 500, 600, 700,
800, 900
• font-size
– absolute-size, relative-size, length, percentage
• font-variant
– small-caps

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Properties - Text
• text-decoration
– underline, line-through
• text-transform
– capitalize, uppercase, lowercase, none
• text-align
– left, right, center, justify
• text-indent
– <length>, <percentage>

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Properties - Position
• position
– absolute, relative
• top
– <length>, <percentage>, auto
• left
– <length>, <percentage>, auto
• Z-index
– <number>, auto

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A few more details
about positioning

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Positioning
• Upper left corner corresponds to (0,0)
• The value of top, bottom, right, left
can be expressed in:
– Length (measured in px, em, etc…)
– Percentage of the parent’s width
(0,0)
Y
X

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The z-index
• stacking order is called the z-index.
• If elements overlap each other, the one
with the higher z-index appears on top.
• Example:
.topElement {position: absolute; z-index=2;
top:0px; left:0px; font-size:36pt; color:red}

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CSS Examples:
• <h1 style="color: white; position:
absolute; bottom: 50px; left: 50px; z-
index: 2"> Text in front.</h1>
– Positioning: Example
– Stacking: Example
– Shadowing: Example
(0,0)
Y
X

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Using Boxes and Positioning for
layout

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In a box:
• Margins are always transparent.
• Borders come in various styles.
• Background settings:
– the area just inside the borders
– includes both the padding and content
areas.

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Examples
img { border-style: ridge;
border-width: 20px;
border-color:red green
blue purple}
h1 {background-color: #CC66FF;
width: 50%;
padding: 20px} H1,50% ,purple background

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Backgrounds
• background-color
– Hex
• background-image
– URL(image.jpg)
• background-repeat
– No-repeat, repeat-x, repeat-y
• background-attachment
– Fixed, scroll
• background-position
– Top, left
• p { background-position: 70px 10px; background-repeat: repeat-
y; background-image: url(background.gif) }
Example

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Background repeat examples:

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Scroll Bar Color
• Example:
<style>
body { color:black;
background-color:#a0a0a0;
scrollbar-face-color:#903030;
scrollbar-arrow-color:#FFFFFF;
scrollbar-track-color:#C0B0B0;
scrollbar-shadow-color:rgb(0,0,0)}
</style>
• CSS generator for scrollbars:
http://www.spectrum-research.com/V2/generators/scr

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Link Style
• a:link {color: #FFFFFF; text-decoration: none}
• a:visited {color: #808080; text-decoration:
none}
• a:hover {color: red; text-decoration: none}

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Cursor
• The cursor property specifies the type
of cursor to be displayed when pointing
on an element.
– Crosshair, hand, move, text, wait, etc.
• Complete demo (cursor styles):
http://www.w3schools.com/css/tryit.asp?filenam

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How-To Examples
(source: w3c)
– examples/css-examples.html

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Linked CSS example:
• You can download these and try on your
own!
• One html file: css_files/htmlcss7.htm
• The external stylesheet:
– css_files/stylecss.css
• The html file can call any stylesheet one
at a time for a different design each time.

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Demos
• http://www.w3schools.com/css/demo_default.h

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CSS templates and tutorials
• http://positioniseverything.net/
• http://positioniseverything.net/guests/3colcom
plex.html
• http://intensivstation.ch/css/en/template.php
• http://www.benmeadowcroft.com/webdev/

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More CSS links
• To create a navigation list design:
http://www.accessify.com/tools-and-
wizards/list-o-matic/list-o-matic.asp
• To create boxes for layout:
http://www.thenoodleincident.com/tutori
als/box_lesson/boxes.html

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