Class 2: CSS Selectors, Classes & Ids

Class 2 Css: seleCtors,
Classes & ids
Web Design , gR APH -327 1- 01
Instructor: Erika Tarte
Rhode Island School of Design
Wintersession 2011

from web content to webpage

In addition to content, webpages contain hidden information that help browsers interpret
structure, meaning, style, interactions, etc.

Most of the visible information takes place in the body of the HTML document, while most
of the hidden formation happens in the head of the HTML document.

Some information happens in external files, like CSS and JavaScript.

We link to these files in the head of the HTML document.

basic html webpage

<html>

<head>

<title>Document Title</title>

</head>

<body>

...

</body>

</html>

what’s css?

CSS Stands for Cascading Style Sheet

Purpose

HTML tells us what to display
CSS tells us how to display

Format

Simple text file
Contains rules for displaying HTML

types of style sheets

Inline Styles

defined within an individual tag
with a lot of content starts to become inefficient

Internal styles

defined at the top of each individual page
with a lot of pages, starts to become inefficient

External styles

defined once for your whole site
all of your html pages link to the same file
extremely efficient (and its what we’ll do in this class)

why external?

Central definition of visual style
make one change, the entire site is updated
can be reused on any number of pages

Developers and designers can work independently

Same content can be restyled for lots of different media
web
print
mobile phone
iPod/iPhone/iPad

characteristics

Cascading
style rules are applied in order
last definition takes precedence over the first

Order of priority
1 browser default lowest priority
2 external styles
3 internal styles
4 inline styles highest priority

linking a css file to your html file

The only change in the HTML file is to add a line of code at the top:

<link rel=”stylesheet” type=”text/css” href=”styles.css” />

Tells browser to include a style sheet called styles.css

You can name the file anything you want (webstyles.css, printstyles.css, awesome.css)

Include the <link> tag just before the </head> tag in your HTML.

basic html webpage w/ link to css file

<html>

<head>

<title>Document Title</title>


</head>

<body>

...

</body>

</html>

linking your first file demo

1 Create a text file and save it as styles.css

2 Add this line to your HTML, right before the </head> tag:


3 Start writing CSS rules in your styles.css file

be prepared...

There are many style properties, don’t worry about memorizing them!

Keep a reference open while coding (www.w3schools.com)

css syntax: vocabulary

selector = what you are defining

curly brackets { } = begin & end of rules for selector

property = set of display properties you can change

value = what you are changing the property to

semicolon ; = ends each rule

css syntax

selector {
property: value;
property: value;
}

css syntax

selector { selec toR is the html element these rules will change

property: value;
property: value;
}

css syntax

selector {
property: value; PRoPeRt y is a display characteristic you are writing a
rule for. Each selector can have multiple properties, and
property: value; some selectors have very specif ic properties.
}

css syntax

selector {
property: value; VAlue is the display characteristic that you want to apply
to the property
property: value;
}

css syntax

sandwich {
cheese: cheddar;
bread: rye;
condiment: mustard;
condiment-style: spicy-brown;
}

css syntax

h1 {
font-family: Helvetica;
font-size: 36px;
font-weight:bold;
text-transform:uppercase;
color:#000000;
}

html class & id attributes

These 2 attributes give you more control over the elements while using CSS

No inherent styles or properties

Different elements can share the same class

IDs are unique, and different elements can’t share them

css class & id selectors

.button {
font-size: 12px;
color: #ff0000;
text-decoration: none;
}

#button1 {
font-size: 12px;
color: #ff0000;
background-color: #ffff00;
}

css class & id selectors

.button {
font-size: 12px;
color: #ff0000;
}

#button1 {
background-color: #ffff00;
}

color values

rgb (red, green, blue)
values 0 to 255
additive color
black: 0,0,0
white: 255,255,255

hexadecimal or “hex"
encoded value of rgb
black: #000000
white: #FFFFFF

css property: color

h1 {
color: rgb(255,255,255);
color: #ffffff;
}

css property: background-color

h1 {
color: #ffffff;
background-color: #000000;
}

fonts

Browsers only display fonts installed on the user’s computer (with some recent exceptions)

To define fonts, the font-family: css property is used

Designers use font-stacking to create prioritized lists of fonts to display

(A safety net, incase the first desired typeface is unavailable)

Start with a very specific typeface, move to a generic classification

css property: font-family

h1 {
color: #ffffff;
font-family: Akkurat, Helvetica, sans-serif;
}

css property: font-size

h1 {
color: #ffffff;
font-size: 72px;
}

css property: font-weight

h1 {
color: #ffffff;
font-size: 72px;
font-weight: normal;
}

css property: letter-spacing

h1 {
color: #ffffff;
font-size: 72px;
letter-spacing: 4px;
}

css property: text-transform

h1 {
color: #ffffff;
font-size: 72px;
letter-spacing: 4px;
text-transform: uppercase;
}

Class 2: CSS Selectors, Classes & Ids

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