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% Getty CodeCamp % Session 3: The Web gets stylish

What is CSS?

  • Cascading Style Sheets
  • A programming language with one job to do: Describing stylistic rules for HTML

Core Concepts

Separation of Concerns

  • HTML for Content, CSS for Presentation
  • This means that the same HTML can be totally transformed by applying a different stylesheet to it. See the CSS Zen Garden for a great example of this.

Rules and the Cascade

  • CSS is organized into rules that define the appearnce of one or more elements on the page.
  • Multiple rules can apply to any given element: you can even define multiple stylesheets.
  • CSS rules will override one another in a process of gradually increasing specificity. This is called the cascade.

Where do I put it?

  • CSS stylesheets can reside in the following places:
  • In an external file ending in .css (this is the best way)
  • In the <head> of your HTML document, inside a <style> tag (sometimes this is okay but external is better)
  • Directly on an HTML element as a style attribute (avoid this)

This is also the order in which overrides are applied; CSS applied directly to an element is very difficult to override, which is one reason we are avoiding it.

What can I do?

CSS can control:

  • color
  • background-color
  • font-size
  • font-family
  • margin
  • padding
  • float
  • display

In 2017, CSS can also be used for transitions, animations, and complicated grid layouts. But we won't cover these in this class.

But even without these newfangled features, the sky is the limit to what CSS can accomplish.

CSS Syntax

Basic Example

/* Selector */
body {
  /* property: value */
  color: #ff0000;
}

Don't forget the closing braces and the semicolons, they're mandatory!

A CSS Rule always starts with a selector (which controls what elements we are targeting with our rule). Inside the {} characters, individual properties are given values.

Selecting multiple elements

/* A rule can target a single element */
h1 {
  font-size: 24px;
}

/* Or multiple elements */
h1, h2, h3, h4, h5, h6 {
  font-family: "Helvetica", "Arial", sans-serif;
}

Valid targets

/* Select HTML elements by name */
body {}
h1 {}
p {}
ol, ul {}

/* Select by class with the "." */
.my-header {}
.page-title {}

/* Select by ID with "#" */
#some-unique-element {}

CSS Examples

HTML Setup

Open up the exercises/ex-3-1-basics.html in Atom and take a look. Open it in your browser too. Start adding some basic style rules in the head of the document to see what happens.

Try these examples

body {
  background-color: #ff0000;
}

h1 {
  font-size: 36px;
}

body {
  font-family: "Comic Sans MS";
}

Typography

Open up the exercises/ex-3-2-typography.html file and follow along.

Font Family

One of the first things you probably want to know is how to get rid of the dreaded Times New Roman, right?

h1, h2, h3, h4, h5, h6 {
  font-family: "Helvetica", "Arial", sans-serif;
}

Any font installed on your machine will work locally, but if you want to make sure that everyone sees the same thing you need to chose fonts carefully.

/* Try this - do you see anything change? */

h1, h2, h3, h4, h5, h6 {
  font-family: "Futura", "Helvetica", "Arial", sans-serif;
}

This is why it's often a good idea to define a series of fonts to act as fallbacks when you declare font-family properties. serif and sans-serif are special keywords that will use whatever the system default is on the user's machine -- good to add this one last, as a last resort.

This page is a good list of some common built-in fonts on Mac and PC systems. Feel free to use any of these in your CSS, just make sure to define fallbacks for users who don't have them installed.

Font Style

You can also specify whether text should be bold, italic, normal, or underlined.

h1, h2, h3, h4, h5, h6 {
  font-family: "Helvetica", "Arial", sans-serif;
  font-weight: bold; /* try italic, normal too */
  text-decoration: underline;
}

Text Alignment

Just like in Word, you can control whether text should be left, center, or right-aligned. You can also justify text (though it looks bad without hyphenation.)

/* possible values: left, right, center, justify */
.body-text p {
  text-align: left;
}

Text spacing

You can control both line-height and letter-spacing in CSS:

/* Small changes go a long way here! */
.body-text p {
  line-height: 1.6;
  letter-spacing: 1px;
}

Font Sizes

The font-size property accepts several different units of measurement, including: px, in, cm, and pt. But most of the time you will want to use em or px.

Hard-coding specific sizes as px values is probably the easiest method, but using em (a relative measurement) can be quite useful.

A common pattern looks like this:

/* Assign a px value to the root element as a baseline */
body {
  font-size: 16px;
}

/* Then set relative values for different parts of the page */
.headings {
  font-size: 0.75em; 
}

.body-text {
  font-size: 1.25em;
}

The em value of these elements will act as a multiplier for the text inside. So we just made all the text in the .heading section 25% smaller, and the .body-text 25% larger, while preserving the relative values of elements to one another.

Colors

  • text: aliceblue, tomato
  • hexadecimal strings (need to start with #): #ff0000, #333333
  • RGB values like rgb(255, 255, 255).

You can find a complete list of predefined color values here

Try writing some rules that change the color of text elements, or the background-color of body, .body-text, or section

Lists

You can control lists too. ol and ul elements can accept many different values for the list-style-type property:

ol {
  list-style-type: lower-roman;
}

ul {
  list-style-type: square
}

/* what happens when you set a value of 'none' ? */

Homework

Take the Recipe document you created in Session 2 and give it some styles! Don't be afraid to add classes to your HTML elements in order to target them more easily with CSS rules.