Learn to Code HTML & CSS 01

Lesson 1: Building Your First Web Page

Contents

  • The difference between HTML and CSS
  • Getting acquainted with HTML elements, tags, and attributes
  • Setting up the structure of your first web page
  • Getting acquainted with CSS selectors, properties, and values
  • Working with CSS selectors
  • Referencing CSS in your HTML
  • The value of CSS resets

What Are HTML & CSS?

HTML, HyperText Markup Language, gives content structure and meaning by defining that content as, for example, headings, paragraphs, or images. CSS, or Cascading Style Sheets, is a presentation language created to style the appearance of content—using, for example, fonts or colors.

The two languages—HTML and CSS—are independent of one another and should remain that way. CSS should not be written inside of an HTML document and vice versa. As a rule, HTML will always represent content, and CSS will always represent the appearance of that content.

Understanding Common HTML Terms

The three common HTML terms you should begin with are elements, tags, and attributes.

Elements

Elements are designators that define the structure and content of objects within a page. Some of the more frequently used elements include multiple levels of headings (identified as h1 through h6 elements) and paragraphs (identified as the <p> element); the list goes on to include the <a>, <div>, <span>, <strong>, and <em> elements, and many more.

Thus, an element will look like the following:

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<a>

Tags

The use of less-than and greater-than angle brackets surrounding an element creates what is known as a tag. Tags most commonly occur in pairs of opening and closing tags.

So, anchor tags will look a bit like this:

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<a>...</a>

Attributes

Attributes are properties used to provide additional information about an element. The most common attributes include the id attribute, which identifies an element; the class attribute, which classifies an element; the src attribute, which specifies a source for embeddable content; and the href attribute, which provides a hyperlink reference to a linked resource.

For example, an <a> element including an href attribute would look like the following:

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<a href="http://shayhowe.com/">Shay Howe</a>

Setting Up the HTML Document Structure

All HTML documents have a required structure that includes the following declaration and elements: <!DOCTYPE html>, <html>, <head>, and <body>.

All of the visible content within the web page will fall within the <body> element. A breakdown of a typical HTML document structure looks like this:

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<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <title>Hello World</title>
  </head>
  <body>
    <h1>Hello World</h1>
    <p>This is a web page.</p>
  </body>
</html>

Code Validation

No matter how careful we are when writing our code, we will inevitably make mistakes. Thankfully, when writing HTML and CSS we have validators to check our work. The W3C has built both HTML and CSS validators that will scan code for mistakes. Validating our code not only helps it render properly across all browsers, but also helps teach us the best practices for writing code.

Understanding Common CSS Terms

In addition to HTML terms, there are a few common CSS terms you will want to familiarize yourself with. These terms include selectors, properties, and values. As with the HTML terminology, the more you work with CSS, the more these terms will become second nature.

Selectors

As elements are added to a web page, they may be styled using CSS. A selector designates exactly which element or elements within our HTML to target and apply styles (such as color, size, and position) to. Selectors may include a combination of different qualifiers to select unique elements, all depending on how specific we wish to be.

Selectors generally target an attribute value, such as an id or class value, or target the type of element, such as <h1> or <p>.

Properties

Once an element is selected, a property determines the styles that will be applied to that element. Property names fall after a selector, within the curly brackets, {}, and immediately preceding a colon.

Values

So far we’ve selected an element with a selector and determined what style we’d like to apply with a property. Now we can determine the behavior of that property with a value. Values can be identified as the text between the colon and semicolon.

Working with Selectors

Selectors, as previously mentioned, indicate which HTML elements are being styled. It is important to fully understand how to use selectors and how they can be leveraged. The first step is to become familiar with the different types of selectors. We’ll start with the most common selectors: type, class, and ID selectors.

Type Selectors

Type selectors target elements by their element type. For example, should we wish to target all division elements, <div>, we would use a type selector of div.

HTML

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<div>...</div>          
<div>...</div>

CSS

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div { ... }

Class Selectors

Class selectors allow us to select an element based on the element’s class attribute value. Class selectors are a little more specific than type selectors, as they select a particular group of elements rather than all elements of one type.

Class selectors allow us to apply the same styles to different elements at once by using the same class attribute value across multiple elements.

Within CSS, classes are denoted by a leading period, ., followed by the class attribute value.

HTML

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<div class="awesome">...</div>
<p class="awesome">...</p>

CSS

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.awesome { ... }

ID Selectors

ID selectors are even more precise than class selectors, as they target only one unique element at a time. Just as class selectors use an element’s class attribute value as the selector, ID selectors use an element’s id attribute value as a selector.

Regardless of which type of element they appear on, id attribute values can only be used once per page. If used they should be reserved for significant elements.

HTML

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<div id="shayhowe">...</div>

CSS

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#shayhowe { ... }

Additional Selectors

Selectors are extremely powerful, and the selectors outlined here are the most common selectors we’ll come across. These selectors are also only the beginning. Many more advanced selectors exist and are readily available. When you feel comfortable with these selectors, don’t be afraid to look into some of the more advanced selectors.

Referencing CSS

In order to get our CSS talking to our HTML, we need to reference our CSS file within our HTML. The best practice for referencing our CSS is to include all of our styles in a single external style sheet, which is referenced from within the <head> element of our HTML document. Using a single external style sheet allows us to use the same styles across an entire website and quickly make changes sitewide.

Consider the following example of an HTML document <head> element that references a single external style sheet.

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<head>
  <link rel="stylesheet" href="main.css">
</head>

Using CSS Resets

Every web browser has its own default styles for different elements. How Google Chrome renders headings, paragraphs, lists, and so forth may be different from how Internet Explorer does. To ensure cross-browser compatibility, CSS resets have become widely used.

There are a bunch of different resets available to use, all of which have their own fortes. One of the most popular resets is Eric Meyer’s reset, which has been adapted to include styles for the new HTML5 elements.

If you are feeling a bit more adventurous, there is also Normalize.css, created by Nicolas Gallagher. Normalize.css focuses not on using a hard reset for all common elements, but instead on setting common styles for these elements. It requires a stronger understanding of CSS, as well as awareness of what you’d like your styles to be.

Cross-Browser Compatibility & Testing

As previously mentioned, different browsers render elements in different ways. It’s important to recognize the value in cross-browser compatibility and testing. Websites don’t need to look exactly the same in every browser, but they should be close. Which browsers you wish to support, and to what degree, is a decision you will need to make based on what is best for your website.

Summary

So far, so good! We’ve taken a few big steps in this lesson.

Just think, you now know the basics of HTML and CSS. As we continue and you spend more time writing HTML and CSS, you’ll become much more comfortable with the two languages.

To recap, so far we’ve covered the following:

  • The difference between HTML and CSS
  • Getting acquainted with HTML elements, tags, and attributes
  • Setting up the structure of your first web page
  • Getting acquainted with CSS selectors, properties, and values
  • Working with CSS selectors
  • Referencing CSS in your HTML
  • The value of CSS resets

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2015 1月 27
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