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Intro to CSS:

Styling Webpages


Girl Develop It is here to provide affordable and accessible programs to learn software through mentorship and hands-on instruction.

Some "rules"

  • We are here for you!
  • Every question is important
  • Help each other
  • Have fun


Tell us about yourself.

  • Who are you?
  • What do you hope to get out of the class?
  • What’s your favorite HTML tag and why?

Anatomy of a Website

Your Content
+ HTML: Structure
+ CSS: Presentation
= Your Website

A website is a way to present your content to the world, using HTML and CSS to present that content & make it look good.

CSS: What Is It?

CSS = Cascading Style Sheets

CSS is a "style sheet language" that lets you style the elements on your page.

CSS is works in conjunction with HTML, but is not HTML itself.

CSS: What Can It Do?

All colored text, position, and size

Screenshot of homepage

CSS: What Does It Look Like?

Screenshot of CSS

The CSS Rule

The CSS Rule

The CSS Rule

selector {
  property: value;
  • A block of CSS code is a rule.
  • The rule starts with a selector.
  • It has sets of properties and values.
  • A property-value pair is a declaration.

Connecting CSS to HTML

3 ways




Connecting CSS to HTML: Inline

<p style="color:red">Some text.</p>
  • Uses the HTML attribute style.
  • Difficult to use in large projects
  • Not preferred.

Connecting CSS to HTML: Embedded

  <style type="text/css">
    p {
      color: blue;
      font-size: 12px;
  • Inside <head> element.
  • Uses <style> tag.
  • Can only be used in one html file

Connecting CSS to HTML: External

  <link rel="stylesheet" type="text/css" href="style.css">
  • Shared resource for several pages.
  • Reduced file size & bandwidth
  • Easy to maintain in larger projects.
  • Preferred by nerds everywhere!

Let's Develop It!

  • In the same folder you used in the HTML class, create a new file called style.css
  • Add a link to the file in the head of your HTML file
  • Add the CSS rule below to the CSS file:
body {
  background-color: yellow;

CSS Syntax

Declarations: Property and value of style you plan to use on HTML element.

Declarations end with a semicolon

Declaration groups are surrounded by curly brackets.

selector {
  property: value;
  property: value;
  property: value;

Selector: Element

p {
  property: value;

Selects all paragraph elements.

img {
  property: value;

Selects all image elements.

CSS Color Values

Your browser can accept colors in many different ways:

  • Color name (ex. red)
  • Hexadecimal value (ex. #FF0000)
  • RGB value (ex. rgb(255, 0, 0))
  • HSL value (ex. hsl(0, 100%, 100%))

The 17 standard colors are: aqua, black, blue, fuchsia, gray, grey, green, lime, maroon, navy, olive, purple, red, silver, teal, white, and yellow.

Property: Color

The color property changes the color of the text.

p {
  color: red;
  color: #ff0000;
  color: rgb(255, 0, 0);

Property: Background-color

The background-color property changes the color of the background.

p {
  background-color: black;
  background-color: #000000;
  background-color: rgb(0,0,0);

Property Values

Each property can have one or more comma separated values.

p {
  color: white;
  background-color: red;
  font-family: Arial, sans-serif;

Property: Font-family

The font-family property defines which font is used.

p {
  font-family: "Times New Roman";
  font-family: serif;
  font-family: "Arial", sans-serif;

Specific font name

Generic name

Comma-separated list

Property: Font-size

The font-size property specifies the size of the font.

p {
  font-size: 12px;
  font-size: 1.5em;
  font-size: 100%;




Property: Fonts (Shorthand)

p {
  font-style: italic;
  font-weight: bold;
  font-size: 10px;
  font-family: sans-serif;
p {
  font: italic bold 10px sans-serif;

Let's Develop It!

  • Add some rules to your css file
  • Change the font color and background color of different types of elements — try selecting links, paragraphs, and lists
  • Change the fonts of your page — try changing the font sizes and styles for different elements

Selector: Position

p em {
  color: yellow;

Selects all em elements that are within a paragraph.

<p>This is <em>important.</em></p>

The associated HTML.

Selector: Position

  • Position selectors are more specific
  • They look for elements inside other elements
  • We seperate nested elements with a space

Selector: Position

So this code:

ul li a strong {
  color: purple;

Means "find a strong tag inside a link inside a list item in an unordered list"

    <a href="programs.html">Our <strong>program</strong></a>

Let's Develop It!

  • In your CSS file, try a position selector
  • Remember, you need to look for an element inside another element

Reusing Code

As a general coding principle, Don't Repeat Yourself.

To reuse CSS, we use IDs and classes.

Recycle symbol

Photo credit: Yo Mostro cc

IDs vs. Classes

ID -- Should only apply to one element on a webpage, i.e., a webpage only has one footer.
The "#" is how you tell CSS "this is an id."

Class -- Lots of elements can have the same class, i.e., There can be many warnings on one webpage.
The "." is how you tell CSS "this is a class name."

Selector: ID

#footer {
  property: value;

Selects all elements with an id of "footer".

<p id="footer">Copyright 2011</p>

The associated HTML.

Selector: Class

.warning {
  color: red;

Selects all elements with a class of "warning".

<p class="warning">Run away!</p>

The associated HTML.

Let's Develop It!

  • Add an ID and class to a your HTML
  • Add CSS rules to target these elements


Styles "cascade" down until changed

p {
  font-family: 'Helvetica';

.red {
  color: red;

#special {
  font-family: Arial;
<p class="red">Paragraph</p>
<p class="red" id="special">Paragraph</p>

Cascading Priority

Your browser assigns different priorities to CSS depending on the type of selector.

  1. Important! - Most Important
  2. In line CSS
  3. ID
  4. Class
  5. Element - Least Important

Cascading Priority

Your browser also assigns priority based on the specificity of the selection. More specific selectors have higher priority.

.main .sale .clearance p { //Most specific
  color: red;

.header .title p {
  color: green;

.footer p { //Least specific
  color: blue;

Cascading Priority

The tie-breaker is position. Rules lower in the file overwrite rules higher in the file

a {
  background-color: yellow;

a {
  background-color: teal;

a { //This rule wins
  background-color: black;

CSS Properties

Many CSS properties have self-explanatory names:

  • background-color
  • font-family
  • font-size
  • color
  • width
  • height

Comprehensive list of all CSS properties


Changing the format of a link when you hover over it is accomplished by using pseudo-classes.

CSS pseudo-classes are used to add special effects to some selectors.


selector:pseudo-class {


a:link {
  text-decoration: none;


a:link  { color:#FF0000; } /* unvisited link */
a:visited { color:#00FF00; } /* visited link */
a:hover, a:focus { color:#FF00FF; } /* mouse over or select with keyboard */
a:active { color:#0000FF; } /* selected link */

a:hover MUST come after a:link and a:visited in the CSS definition to be effective!

a:active MUST come after a:hover in the CSS definition to be effective!

Let's Develop It!

Add pseudo classes to your links