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- Herausgeber: John Wiley & Sons
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
Everything you need to build websites with the newest versions of HTML and CSS
If you develop websites, you know that the goal posts keep moving, especially now that your website must work on not only traditional desktops, but also on an ever-changing range of smartphones and tablets. This step-by-step book efficiently guides you through the thicket. Teaching you the very latest best practices and techniques, this practical reference walks you through how to use HTML5 and CSS3 to develop attractive, modern websites for today's multiple devices. From handling text, forms, and video, to implementing powerful JavaScript functionality, this book covers it all.
- Serves as the ultimate beginners guide for anyone who wants to build websites with HTML5 and CSS3, whether as a hobbyist or aspiring professional developer
- Covers the basics, including the different versions of HTML and CSS and how modern websites use structure and semantics to describe their contents
- Explains core processes, such as marking up text, images, lists, tables, forms, audio, and video
- Delves into CSS3, teaching you how to control or change the way your pages look and offer tips on how to create attractive designs
- Explores the jQuery library and how to implement powerful JavaScript features, such as tabbed content, image carousels, and more
Get up to speed on HTML5, CSS3, and today's website design with this practical guide. Then, keep it on your desk as a reference!
Das E-Book können Sie in Legimi-Apps oder einer beliebigen App lesen, die das folgende Format unterstützen:
Veröffentlichungsjahr: 2013
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Table of Contents
Cover
Chapter 1: Structuring Documents for the Web
A Web of Structured Documents
Introducing HTML5
Attribute Groups
Core Elements
Basic Text Formatting
Understanding Block and Inline Elements
Grouping Content
Working with Lists
Summary
Chapter 2: Fine-tuning Your Text
Elements That Describe Text-Level Semantics
Editing Text
Using Character Entities for Special Characters
Comments
Summary
Chapter 3: Links and Navigation
Basic Links
Understanding Directories and Directory Structures
Understanding URLs
Creating In-Page Links with the <a> Element
Advanced E-mail Links
Summary
Chapter 4: Images, Audio, and Video
Adding Images Using the <img> Element
Using Images as Links
Choosing the Right Image Format
Adding Flash, Video, and Audio to Your Web Pages
Summary
Chapter 5: Tables
Introducing Tables
Basic Table Elements and Attributes
Adding a Caption to a Table
Grouping Sections of a Table
Nested Tables
Accessible Tables
Summary
Chapter 6: Forms
Introducing Forms
Creating a Form with the <form> Element
Form Controls
Creating a Contact Form
Creating Labels for Controls and the <label> Element
Structuring Your Forms with <fieldset> and <legend> Elements
Focus
Disabled and Read-Only Controls
Sending Form Data to the Server
Creating More Usable Form Fields
Summary
Chapter 7: Cascading Style Sheets
Introducing CSS
Where You Can Add CSS Rules
CSS Properties
Controlling Text
Text Formatting
Text Pseudo-Classes
Styling Text
Selectors
Lengths
Introducing the Box Model
Creating a Style Sheet for Code
Summary
Chapter 8: More Cascading Style Sheets
Links
Backgrounds
Lists
Tables
Outlines
The :focus and :active Pseudo-Classes
Generated Content
Miscellaneous Properties
Additional Rules
Positioning and Layout with CSS
Summary
Chapter 9: Rounded Corners, Animations, Custom Fonts, and More with CSS3
The Modular Approach of CSS3
Mature CSS3 Modules
New and In-Development Modules
Summary
Chapter 10: Learning JavaScript
What Is Programming About?
How to Add a Script to Your Pages
Create an External JavaScript
The Document Object Model
Starting to Program with JavaScript
Variables
Operators
Functions
Conditional Statements
Looping
Events
Built-in Objects
Writing JavaScript
Summary
Chapter 11: Working with jQuery
Why jQuery?
Adding jQuery to Your Page
jQuery Basics
jQuery and the DOM
Managing Events with jQuery
Summary
Chapter 12: jQuery: Beyond the Basics
Ajax with jQuery
jQuery UI
Summary
Chapter 13: Checklists
Search Engine Optimization Checklist
Accessibility Checklist
Appendix A: Answers to Exercises
Chapter 1
Chapter 2
Chapter 3
Chapter 4
Chapter 5
Chapter 6
Chapter 7
Chapter 8
Chapter 9
Chapter 10
Chapter 11
Chapter 12
Chapter 13
Appendix B: HTML Element Reference
Appendix C: CSS Properties
Font Properties
Text Properties
Color and Background Properties
Border Properties
Dimensions
Margin Properties
Padding Properties
List Properties
Positioning Properties
Outline Properties
Table Properties
Classification Properties
Internationalization Properties
Selected CSS3 Properties
Lengths
Appendix D: Color Names and Values
Using Hex Codes to Specify Colors
Understanding Hex Codes
Using Color Names to Specify Colors
Color Name and Number Reference
Appendix E: Character Encodings
Appendix F: Special Characters
Character Entity References for ISO 8859-1 Characters
Character Entity References for Symbols, Mathematical Symbols, and Greek Letters
Character Entity References for Markup-Significant and Internationalization Characters
Appendix G: Language Codes
Appendix H: MIME Media Types
Text
Image
Multipart
Audio
Video
Message
Model
Application
Appendix I: Changes between HTML4 and HTML5
New Elements
New <input> Element Types
New Attributes
Global Attributes
Changed Attributes
Obsolete Elements
Obsolete Attributes
At-Risk Elements
About the Author
Credits
Acknowledgments
Introduction
EULA
Chapter 1
Structuring Documents for the Web
What You Will Learn in This Chapter
Creating several example web pages in HTML
Seeing how a web page describes its structure to a web browser
Discovering the meaning of some key terms used by web designers, such as elements
,
attributes
,
tags
,
andmarkup
Wrox.com Code Downloads for this Chapter
The wrox.com code downloads for this chapter are found at www.wrox.com/remtitle.cgi?isbn=9781118340189 on the Download Code tab. The code is in the Chapter 1 download and individually named according to the names throughout the chapter.
In this chapter, you learn the key concept to create any web page: how to give it structure. You need to add structure to a document so that web browsers can present the page to people who visit your site in a way they can understand. For example, imagine a news article that contains a headline (or title) and several paragraphs of text; if you want to put this article on the web, you would need to add structure to the words in the document so that the browser knows which words are the headline, and where each paragraph starts and ends. To give a document structure, you need to learn how to create web pages using HTML.
A Web of Structured Documents
Every day, you come across all kinds of printed documents—newspapers, train timetables, and insurance forms. You can think of the web as being a sea of documents that all link together and bear a strong similarity to the printed documents that you meet in everyday life.
Take the example of a newspaper. A newspaper consists of several stories or articles (and probably a fair smattering of advertisements, too). Each story has a headline and then some paragraphs, perhaps a subheading, and then some more paragraphs; it may also include a picture or two.
The structure of articles on news websites is similar to the structure of articles in newspapers. Each article consists of headings, paragraphs of text, and some pictures. (Sometimes the pictures might be replaced by a video.) The parallel is quite clear; the only difference is that in a newspaper you may have several stories on a single page, whereas on the web each story tends to get its own page. The news websites also often use homepages that display the headline and a brief summary of the stories.
Consider another example: You’re catching a train to see a friend, so you check the schedule or timetable to see what time the train leaves. The main part of the schedule is a table telling you what times trains arrive and when they depart from different stations. You can probably think of several types of documents that use tables. From the listings in the financial supplement of your paper to the TV schedule, you come across tables of information every day—and often when this information is put on the web, these tables are re-created.
Another common type of printed document is a form. For example, think about a common form from an insurance company. Such a form contains fields to write your name, address, and the amount of coverage, along with check boxes to indicate the number of rooms in the house and what type of lock is on the front door. There are lots of forms on the web, from simple search boxes that ask what you are looking for to the registration forms you are required to fill out before you can place an online order for books or CDs.
As you can see, there are many parallels between the structure of printed documents you come across every day and pages you see on the web. When you are writing web pages, it is the HTML code you start learning in this chapter that tells the web browser how the information you want to display is structured—what text to put in a heading, paragraph, or table, and so on so that the browser can present it properly to the user.
Introducing HTML5
Even if you have never seen any HyperText Markup Language (HTML) code, you may know that it is used to create web pages. There have been five versions of HTML since the web began, and the development of the language is overseen by an organization called the World Wide Web Consortium (W3C).
This book focuses on the latest version of the language, popularly referred to as HTML5. There are two other versions you might encounter. These are HTML 4.01, the last major version of the language from December 1999, and a stricter version from 2000 called Extensible HyperText Markup Language (XHTML). XHTML is still popular in some applications, so important differences between it and HTML5 will be called out in the text.
As its name suggests, HTML is a markup language, which may sound complicated until you realize that you come across markup every day. When creating a document in a word processor, you can add styles to the text to explain the document’s structure. For example, you can distinguish headings from the main body of the text using a heading style (usually with a larger font). You can use the Return (or Enter) key to start a new paragraph. You can insert tables into your document to hold data or create bulleted lists for a series of related points, and so on. Although this does affect the presentation of the document, the key purpose of this kind of markup is to provide a structure that makes the document easier to understand.
When marking up documents for the web, you perform a similar process, except you do it by adding things called tags to the text. With HTML, the key thing to remember is that you must add the tags to indicate the structure of the document (not how you want it to be presented); for example, which part of the document is a heading, which parts are paragraphs, what belongs in a table, and so on. Browsers such as Internet Explorer, Firefox, and Google Chrome all use this markup to help present the text in a familiar fashion, similar to that of a word processor—main headings are bigger than the text in paragraphs, there is space above and below each paragraph, and lists of bullet points have a circle in front of them.
Now have a look at a simple web page (ch01_eg01.html). You don’t need any special programs to write web pages; you can simply use a text editor such as Notepad on Windows or TextEdit on a Mac and save your files with the .html or .htm file extension.
<html> <head> <title>Popular Websites: Google</title> </head> <body> <h1>About Google</h1> <p>Google is best known for its search engine, although Google now offers a number of other services.</p> <p>Google's mission is to organize the world's information and make it universally accessible and useful.</p> <p>Its founders Larry Page and Sergey Brin started Google at Stanford University.</p> </body> </html>
This may look a bit confusing at first, but it will all make sense soon. As you can see, there are several sets of angle brackets with words or letters between them, such as <html>, <head>, </title>, and </body>. These angle brackets and the words inside them are known as tags, and these are the markup previously mentioned. Figure 1-1 illustrates what this page would look like in a web browser.
Figure 1-1
As you can see, this document contains the heading “About Google” and a paragraph of text to introduce the company. Note also that it says “Popular Websites: Google” in the top-left corner of the browser window; this is known as the title of the page (to the right it says Mozilla Firefox, which is the browser this page was opened in).
To understand the markup in this first example, you need to look at what is written between the angle brackets and compare that with what you see in the figure, which is what you do next.
Tags and Elements
If you look at the first and last lines of the code for the previous example, you see pairs of angle brackets containing the letters “html”. Starting on the first line, the first angled bracket looks like a less-than sign (<); then there are the letters “html,” followed by a second angled bracket, which looks like a greater-than sign (>). The two brackets and all the characters between them are known as a tag.
In this example, there are lots of tags, and they are all in pairs; there are opening tags and closing tags. The closing tag is always slightly different from the opening tag in that it has a forward slash (/) after the first angled bracket: </html>.
A pair of tags and the content these include are known as an element. In Figure 1-2, you see the heading for the page of the previous example.
Figure 1-2
The opening tag says, “This is the beginning of a heading” and the closing tag says, “This is the end of a heading.” Like most tags in HTML, the text inside the angled brackets explains the purpose of the tag—here h1 indicates that it is a level 1 heading (or top-level heading). As you will see shortly, there are also tags for subheadings (<h2>, <h3>, <h4>, <h5>, and <h6>). If you don’t put tags around the words “About Google,” it is just another bit of text; it would not be clear that these words formed the heading.
Now look at the three paragraphs of text about the company; each one is placed between an opening <p> tag and a closing </p> tag. And you guessed it, the p stands for paragraph.
As you can see, the tags throughout this example actually describe what you will find between them, creating the structure of the document. The text between the <h1> and </h1> tags is a heading, and the text between the opening <p> and closing </p> tags makes up paragraphs. Indeed, the whole document is contained between opening <html> and closing </html> tags.
You often find that terms from a family tree are used to describe the relationships between elements. For example, an element that contains another element is known as the parent, whereas the element that’s between the parent element’s opening and closing tags is called a child of that element. So, the <title> element is a child of the <head> element, the <head> element is the parent of the <title> element, and so on. Furthermore, the <title> element can be thought of as a grandchild of the <html> element.
Additionally, if two elements are children of the same parent, they are referred to as siblings.
It is worth noting that the tags in this example are all in lowercase characters; you sometimes see web pages written in HTML where tags are uppercase (or a mix of uppercase and lowercase letters). When XHTML was introduced, with its stricter rules, it stated that all tags were written in lowercase. Technically, HTML5 loosens these restrictions to enable mixed case. In practice you generally see lowercase even in HTML5 documents.
Separating Heads from Bodies
Whenever you write a web page in HTML, the whole of the page is contained between the opening <html> and closing </html> tags, just as it was in the previous example. Inside the <html> element, there are two main parts to the page:
The
<head>
element:
Often referred to as the head of the page, this contains information
about
the page. (This is not the main content of the page.) For example, it might contain a title and a description of the page or instructions on where a browser can find CSS rules that explain how the document should look. It consists of the opening
<head>
tag, the closing
</head>
tag, and everything in between.
The
<body>
element:
Often referred to as the body of the page, this contains the information you actually see in the main browser window. It consists of the opening
<body>
tag, the closing
</body>
tag, and everything in between.
Together, the <html>, <head>, and <body> elements make up the skeleton of an HTML document—they are the foundation upon which every web page is built.
Inside the <head> element of the first example page, you see a <title> element:
<head> <title>Popular Websites: Google</title> </head>
Between the opening <title> tag and the closing </title> tag are the words “Popular Websites: Google,” or the title of this web page. Figure 1-1 shows the words at the top of the browser window, which is where browsers such as Internet Explorer, Firefox, and Chrome display the title of a document. It is also the name they use when you save a page in your Favorites List, and it helps search engines understand what your page is about. The <title> element is mandatory for all web pages.
The real content of your page is held in the <body> element, which is what you want users to read, and this is shown in the main browser window.
You may have noticed that the tags in this example appear in a symmetrical order. If you want to have one element inside another, both the element’s opening and closing tags must be inside the containing element. For example, the following is allowed:
<p> This paragraph contains some <em>emphasized text.</em></p>
whereas the following is wrong because the closing </em> tag is not inside the paragraph element:
<p> This paragraph contains some <em>emphasized text. </p></em>
In other words, if an element is to contain another element, it must wholly contain that element. This is referred to as nesting your elements correctly.
Attributes Tell You about Elements
Attributes in HTML are much like the attributes you experience every day. They are the qualities that describe a person or thing, such as a tall man or a brown dog. Similarly, HTML elements can be described in ways that web browsers can understand. This section looks at attributes, starting with the most important one that beats at the heart of the web.
What differentiates web documents from standard documents are the links (or hyperlinks) that take you from one web page to another. Look at a link by adding one to the example you just looked at. Links are created using an <a> element. (The a stands for anchor.)
You can add a link from this page to Google in a new paragraph at the end of the document. There is just one new line in this example (ch01_eg02.html) and that line is highlighted:
<html> <head> <title>Popular Websites: Google</title> </head> <body> <h1>About Google</h1> <p>Google is best known for its search engine, although Google now offers a number of other services.</p> <p>Google's mission is to organize the world's information and make it universally accessible and useful.</p> <p>Its founders Larry Page and Sergey Brin started Google at Stanford University.</p>
<p><a href="http://www.Google.com/">Click here to visit Google's Web
site.</a></p>
</body> </html>
Inside this new paragraph is the <a> element that creates the link. Between the opening <a> tag and the closing </a> tag is the text that you can click, which says, “Click here to visit Google’s Web site.” Figure 1-3 shows you what this page looks like in a browser.
Figure 1-3
If you look closely at the opening tag of the link, it carries something called an attribute. In this case, it’s the href attribute; this is followed by an equal sign and then a pair of quotation marks, which contain the URL for Google’s website. In this case, the href attribute tells you where the link should take you. You look at links in greater detail in the Chapter 3, “Links and Navigation,” but for the moment this illustrates the purpose of attributes.
Attributes are used to say something about the element that carries them, and they always appear on the opening tag of the element that carries them. Almost all attributes consist of two parts: a name and a value. The
name
is the property of the element that you want to set. In this example, the
<a>
element carries an attribute whose name is
href
, which you can use to indicate where the link should take you.
The
value
is what you want the value of the property to be. In this example, the value was the URL of the site that the link should take you to, so the value of the
href
attribute is
http://www.google.com.
The value of the attribute should always be put in double quotation marks and separated from the name with the equal sign.
There are several attributes in HTML5 that do not consist of a name/value pair but consist of just a name. These are called boolean attributes and you will learn more about those in the section “Attribute Groups.”
Another common attribute on anchors is the title attribute, which gives a plain language description of the target of the link. You could add one to the example to inform people that Google is a popular search engine.
<a href="http://www.Google.com" title="Google.com is the world's most popular search engine">
This illustrates that elements can carry several attributes; although, an element should never have two attributes of the same name.
Learning from Others by Viewing Their Source Code
When HTML first came out, a lot of people learned how to create pages by using a handy feature that you can find in most common browsers: the ability to look at the source code that made the page.
If you go to the View menu in your browser and then look for an option that says View Source or Page Source, you should see the code that created the page.
If you want to see how the author of a page achieved something on a page, this can be a handy technique. Figure 1-4 shows how to look at the source of the author’s homepage. (The window on the right contains the source for the page.)
Figure 1-4
Elements for Marking Up Text
You now know that an HTML page (also sometimes referred to as an HTML document) consists of elements that describe how its content is structured. Each element describes what you will find between its opening and closing tags. The opening tags can also carry attributes that tell you more about that particular element.
Equipped with this knowledge, you can find that much of learning HTML is a matter of learning what elements you can use, what each of these elements does, and what attributes each can carry.
Attribute Groups
As you have seen, attributes live on the opening tag of an element and provide extra information about the element that carries them. Many attributes consist of a name and a value; the name reflects a property of the element the attribute describes, and the value is a value for that property. For example, the lang attribute describes the language used within that element; a value such as EN-US would indicate that the language used inside the element is U.S. English.
Some attributes consist of only a name, such as required or checked. These are called boolean attributes. To say something is a boolean (which you learn more about in Chapter 10, “Learning JavaScript”) is to indicate that it can be in one of two states: true or false. For HTML attributes the presence of one of the boolean attributes in a tag indicates that the value is true. So, the following are equivalent:
<input type="text" required > <input type="text" required="true">
Many of the elements in HTML can carry some or all the attributes you will meet in this section. At first some of them may sound a little abstract; although, they will make more sense as you see them used throughout the book. So don’t worry if they do not make much sense at first.
In this section, you look at three groups of attributes common to many HTML elements:
Core attributes:
Including the
class
,
id
,
style
, and
title
attributes
Internationalization attributes:
For example, the
dir
and
lang
attributes
Accessibility attributes:
For example,
accesskey
and
tabindex
Core Attributes
The four core attributes that you can use on the majority of HTML elements (although not all) are:
id title class style
Throughout the rest of the book, these attributes are revisited when they have special meaning for an element that differs from the description given here; otherwise their use can generally be described as you see in the subsections that follow.
The id Attribute
You can use the id attribute to uniquely identify any element within a page. You might want to uniquely identify an element so that you can link to that specific part in the document or to specify that a CSS style or piece of JavaScript should apply to the content of just that one element within the document.
The syntax for the id attribute is as follows (where string is your chosen value for the attribute):
id="string"
For example, you can use the id attribute to distinguish between two paragraph elements, like so:
<p id="accounts">This paragraph explains the role of the accounts department.</p> <p id="sales">This paragraph explains the role of the sales department.</p>
Following are some special rules for the value of the id attribute:
Must begin with a letter (A–Z or a–z) and can then be followed by any number of letters, digits (0–9), hyphens, underscores, colons, and periods. (You may not start the value with a digit, hyphen, underscore, colon, or period.)
Must remain unique within that document; no two
id
attributes may have the same value within one HTML page. This case should be handled by the
class
attribute.
The class Attribute
You can use the class attribute to specify that an element belongs to a class of elements. For example, you might have a document that contains many paragraphs, and a few of those paragraphs might contain a summary of key points, in which case you could add a class attribute whose value is summary to the relevant <p> elements to differentiate those paragraphs from the rest in the document.
<p class="summary">Summary goes here</p>
It is commonly used with CSS, so you learn more about the use of the class attribute in Chapter 7, which introduces CSS. The syntax of the class attribute is as follows:
class="className"
The value of the attribute may also be a space-separated list of class names, for example:
class="className1 className2 className3"
The title Attribute
The title attribute gives a suggested title for the element. The syntax for the title attribute is as follows:
title="string"
The behavior of this attribute depends upon the element that carries it; although, it is often displayed as a tooltip or while the element loads. Not every element that can carry a title attribute actually needs one, so when you meet an element that particularly benefits from use of this attribute, you will see the behavior it has when used with that element.
The style Attribute
The style attribute enables you to specify CSS rules within the element. You meet CSS in Chapter 7, but for now, here is an example of how it might be used:
<p style="font-family:arial; color:#Fc00f000;">Some text.</p>
As a general rule, however, it is best to avoid the use of this attribute. If you want to use CSS rules to govern how an element appears, it is better to use a separate style sheet instead. The only place where this attribute is still commonly used is when it is set with JavaScript. You learn more about that in Chapter 11, “Working with jQuery,” when you’re introduced to jQuery’s powerful tools for manipulating HTML elements.
Internationalization
The web is a worldwide phenomenon. Because of this, there are mechanisms built into the tools that drive the web that allow authors to create documents in different languages. This process is called internationalization.
Two common internationalization attributes help users write pages for different languages and character sets:
dir lang
You look at each next, but it is worth noting that even in current browsers, support for these attributes is still patchy. Therefore where possible you should specify a character set that creates text in the direction you require.
The website of a helpful W3C document that describes internationalization issues in greater detail is found at www.w3.org/TR/i18n-html-tech-char/; although, you briefly look at each of these attributes next.
The dir Attribute
The dir attribute enables you to indicate to the browser the direction in which the text should flow: left to right or right to left. When you want to indicate the directionality of a whole document (or the majority of the document), use it with the <html> element rather than the <body> element for two reasons: Its use on the <html> element has better support in browsers, and it can apply to the header elements as well as those in the body. You can also use the dir attribute on elements within the body of the document if you want to change the direction of a small portion of the document.
The dir attribute can take one of two values, as you can see in Table 1-1.
Table 1-1: dir Attribute Values
Value
Meaning
ltr
Left to right (the default value)
rtl
Right to left (for languages such as Hebrew or Arabic that are read right to left)
The lang Attribute
The lang attribute enables you to indicate the main language used in a document.
The lang attribute was designed to offer language-specific display to users; although, it has little effect in the main browsers. The benefits of using the lang attribute are for search engines (which can tell the user which language the document is authored in), screen readers (which might need to pronounce different languages in different ways), and applications (which can alert users when either they do not support that language or it is a different language than their default language). When used with the <html> element, the attribute applies to the whole document; although, you can use it on other elements, in which case it just applies to the content of those elements.
The values of the lang attribute are ISO-639-1 standard two-character language codes. If you want to specify a dialect of the language, you can follow the language code with a dash and a subcode name. Table 1-2 offers some examples.
Table 1-2: lang Attribute Values
Value
Meaning
ar
Arabic
en
English
en
-us
U.S. English
zh
Chinese
You can find a list of language codes for most of the main languages in use today in Appendix G, “Language Codes.”
Core Elements
Now take a closer look at the four main elements that form the basic structure of every document: <html>, <head>, <title>, and <body>. These four elements should appear in every HTML document that you write, and you will see them referred to throughout this book as the skeleton of the document.
About DOCTYPEs
Although the four main elements describe the skeleton of a document, one final piece qualifies the document as a whole. The DOCTYPE (for DOCument TYPE) tells the browser what rules to follow when showing the document to the user. These rules are called modes. This book focuses on the HTML5 DOCTYPE that puts the browser into strict mode. You can think of strict mode as the browser acknowledging the author wanting to play by the rules. The other common mode, quirks mode, tells the browser you will use some funky rules, which have their origins in the late 1990s. You don’t want to have anything to do with quirks mode.
So what does the HTML5 DOCTYPE look like?
<!doctype html>
Start all your documents with that DOCTYPE, and your pages will always render in the correct mode.
The basic skeleton of an HTML5 page therefore looks like this:
<!doctype html> <html> <head> <title>The Skeleton of an HTML5 Document</title> </head> <body> </body> </html>
The <html> Element
The <html> element is the containing element for the whole HTML document. After the DOCTYPE declaration, each HTML document should have an opening <html> tag, and each document should end with a closing </html> tag.
The <html> element can also carry the following attributes, which you learned about in the “Attribute Groups” section:
id dir lang
The <head> Element
The <head> element is just a container for all other header elements. It is the first thing to appear after the opening <html> tag.
Each <head> element should contain a <title> element indicating the title of the document; although, it may also contain any combination of the following elements, in any order:
<
base
>
, which you will meet in Chapter 3, “Links and Navigation”
<
link
>
to link to an external file, such as a style sheet, which you see in Chapter 7
<
style
>
to include CSS rules inside the document, covered in Chapter 7
<
script
>
for including script in the document, which you see in more detail in Chapter 10
<
meta
>
, which includes information about the document such as a description or the name of the author
The opening <head> tag can carry the following attributes:
id dir lang
The <title> Element
You should specify a title for every page that you write using the <title> element (which, as you saw earlier in the chapter, is a child of the <head> element). It is presented and used in several ways:
At the top of a browser window (as you saw in the first example and
Figure 1-1
)
As the default name for a bookmark in browsers such as IE, Firefox, and Chrome
By search engines that use its content to help index pages
Therefore, you must use a title that describes the content of your site. For example, the homepage of this book should not just say “Homepage”; rather it should describe what your site is about. Rather than just saying “Wrox Homepage,” it is more helpful to write:
<title>Wrox: Programming Books, Learn HTML, CSS, ASP.Net, PHP</title>
The test for a good title is whether visitors can tell what they will find on that page just by reading the title, without looking at the actual content of the page, and whether it uses words that people would use if they were going to search for this kind of information.
The <title> element should contain only the text for the title; it may not contain any other elements. The <title> element can carry the following attributes:
id dir lang
Links and Style Sheets
Although you’ll learn more about CSS and JavaScript later in the book, they are going to be a common element on every page you look at and build, so it’s important that we quickly cover how to include them in your web pages.
Adding a style sheet relies on the <link> element. The <link> element also uses the href attribute, which you learned about already, to point to a resource on the web. In this case, instead of pointing to a new page or website to visit when a link is clicked, it points to the location of a file containing style information for the current page. The rel (for relation) attribute indicates that the linked document is a style sheet and should be handled accordingly.
<link rel="stylesheet" href="css/main.css">
Adding a script to the page is even easier. You add a <script> element to the page and add a src attribute pointing to the location of the JavaScript file you want to use.
<script src="js/main.js"></script>
You need to start using one piece of JavaScript. Now that you know how to add a script to the page, you’re ready to learn about the HTML5 Shiv and Modernizr.
Ensuring Backward Compatibility for HTML5 Tags
There’s one final element you see in many HTML5 documents. Because of a wrinkle in the way that Internet Explorer deals with unknown HTML elements, you need to include a small piece of JavaScript in the head of your document. If you don’t, things look wrong when you view your pages in Internet Explorer 8 or less. It’s called the HTML5 Shiv, and including it in your pages looks something like this:
<script src="http://cdnjs.cloudflare.com/ajax/libs/html5shiv/3.6/html5shiv.min.js"> </script>
As for what it does, for the time being, just know that it needs to be there, or you’ll get unpredictable results in IE8 and older.
If you’re interested in the history of this small but vitally important script, see Paul Irish’s article, “The History of the HTML5 Shiv,” at http://paulirish.com/2011/the-history-of-the-html5-shiv/.
Building on the HTML5 Shiv, there’s another library you’ll encounter in this book. It’s called Modernizr and at its core includes the HTML5 Shiv for backward compatibility; in addition, it adds in tests for emerging web features that you can use when building sites. That way you can ensure that you’re not trying to serve something to a browser that can’t actually handle it. You’ll learn about Modernizr throughout the book, but for now the following code sample shows how to include Modernizr:
<script src="http://cdnjs.cloudflare.com/ajax/libs/modernizr/2.6.1/modernizr.min.js"> </script>
The power of Modernizr will become more apparent throughout the book. For now the examples in the book use the simpler HTML5 Shiv to ensure compatibility with Internet Explorer 8 and below.
And now, with that trip through the head, you’re ready to start adding in the star of the show, the content of your page.
The <body> Element
The <body> element appears after the <head> element, and as you have already seen, it contains the part of the web page that you actually see in the main browser window, which is sometimes referred to as body content. The <body> element can carry all the attributes from the attribute groups.
Common Content Elements
You spend most of the remaining part of this chapter learning the different elements you can use to describe the structure of text. These include:
The six levels of headings:
<h1>
,
<h2>
,
<h3>
,
<h4>
,
<h5>
, and
<h6>
Paragraphs
<p>
, preformatted sections
<pre>
, line breaks
<
br
/>
, and addresses
<address>
Grouping elements:
<div>
,
<header>
,
<hgroup>
,
<nav>
,
<section>
,
<article>
, and
<hr>
Presentational elements:
<b>
,
<
i
>
,
<sup>
, and
<sub>
Phrase elements:
<
em
>
,
<strong>
,
<
abbr
>
,
<
dfn
>
,
<
blockquote
>
,
<q>
,
<cite>
,
<code>
,
<
kbd
>
,
<
var
>
, and
<
samp
>
Lists such as unordered lists using
<
ul
>
and
<li>
; ordered lists using
<
ol
>
and
<li>
; and definition lists using
<dl>
,
<
dt
>
, and
<
dd
>
Editing elements:
<ins>
and
<del>
That may sound like a lot of elements, but you might be surprised at how quickly you can move through them.
Basic Text Formatting
Because almost every document you create contains some form of text, the elements you are about to meet are likely to feature in most pages that you will build. In this section, you learn how to use basic text formatting elements:
<
h1
>
,
<h2>
,
<h3>
,
<h4>
,
<h5>
, and
<h6>
<
p
>
,
<
br
>
, and
<pre>
As you read through this section, one browser might display each of these elements in a certain way, and another browser might display the same page in a slightly different way. For example, the typefaces used, the font sizes, and the spaces around these elements may differ between browsers. (And therefore the amount of space a section of text takes up can vary, too.)
Before you look at the elements, it helps to know how text displays by default without any elements. This helps demonstrate the importance to use markup to tell the browser if you want it to treat text differently.
White Space and Flow
Before you start to mark up your text, it’s best to understand what HTML does when it comes across spaces and how browsers treat long sentences and paragraphs of text.
You might think that if you put several consecutive spaces between two words, the spaces would appear between those words onscreen, but this is not the case; by default, only one space displays. This is known as white space collapsing. Similarly, if you start a new line in your source document, or you have consecutive empty lines, these will be ignored and simply treated as one space, as will tab characters. For example, consider the following paragraph (taken from ch01_eg03.html in the code samples):
<p>This paragraph shows how multiple spaces between words are treated as a single space. This is known as white space collapsing, and the big spaces between some of the words will not appear in the browser. It also demonstrates how the browser will treat multiple carriage returns (new lines) as a single space, too.</p>
In Figure 1-5 the browser treats the multiple spaces and several carriage returns (where text appears on a new line) as if there were only one single space. It also enables the line to take up the full width of the browser window.
Now look at the code for this example again, and compare where each new line starts in the code with where each new line starts onscreen. Unless told otherwise, when a browser displays text, it automatically takes up the full width of the screen and wraps the text onto new lines when it runs out of space (refer to Figure 1-5). You can see the effect of this better if you open this example in a browser and try resizing the browser window (making it smaller and larger) and notice how the text wraps at new places on the screen. (This example is available with the rest of the download code for this book at www.wrox.com.)
Figure 1-5
White space collapsing can be particularly helpful because it enables you to add extra spaces into your HTML that do not show up when viewed in a browser. You can use these spaces to indent your code, which makes it easier to read. The first two examples in this chapter demonstrated indented code, where child elements are indented from the left to distinguish them from their parent elements, which is used this throughout this book to make the code more readable. (If you want to preserve the spaces in a document, you need to use either the <pre> element, which you learn about later in the chapter, or an entity reference such as , a nonbreaking space, which you learn about in Appendix F, “Special Characters.”)
Now that you know how multiple spaces and line breaks are collapsed, you can see why you must learn how to use the elements in the rest of this chapter to break up and control the presentation of your text.
Creating Headings Using <hn> Elements
No matter what sort of document you create, most documents have headings in one form or another. Newspapers use headlines; a heading on a form tells you the purpose of the form; the title of a table of sports results tells you the league or division the teams play in; and so on.
In longer pieces of text, headings can also help structure a document. If you look at the table of contents for this book, you can see how different levels of headings have been arranged to add structure to the book, with subheadings under the main headings.
HTML offers six levels of headings, which use the elements <h1>, <h2>, <h3>, <h4>, <h5>, and <h6>. Browsers display the <h1> element as the largest of the six and <h6> as the smallest. (Although you can see in Chapter 7 that you can use CSS to override the size and style of any of the elements.) The levels of headings would look something like those in Figure 1-6 (ch01_eg04.html).
Figure 1-6
Here is another example of how you might use headings to structure a document (ch01_eg05.html), where the <h2> elements are subheadings of the <h1> element. (This actually models the structure of this section of the chapter.)
<h1>Basic Text Formatting</h1>
<p> This section is going to address the way in which you mark up text. Almost every document you create will contain some form of text, so this will be a very important section. </p>
<h2>White Space and Flow</h2>
<p> Before you start to mark up your text, it is best to understand what HTML does when it comes across spaces and how browsers treat long sentences and paragraphs of text.</p>
<h2>Creating Headings</h2>
<p> No matter what sort of document you are creating, most documents have headings in some form or other...</p>
Figure 1-7 shows how this will look.
Figure 1-7
The six heading elements can all carry the universal attributes:
class id style title dir lang
Creating Paragraphs Using the <p> Element
The <p> element offers another way to structure your text. Each paragraph of text should go in between an opening <p> and closing </p> tag, as in this example (ch01_eg06.html):
<p>Here is a paragraph of text.</p> <p>Here is a second paragraph of text.</p> <p>Here is a third paragraph of text.</p>
When a browser displays a paragraph, it usually inserts a new line before the next paragraph and adds a little bit of extra vertical space, as shown in Figure 1-8.
Figure 1-8
The <p> element can carry all the universal attributes:
class id style title dir lang
Creating Line Breaks Using the <br> Element
Whenever you use the <br> element, anything following it starts on the next line. The <br> element is an example of an empty element; you don’t need opening and closing tags, because there is nothing to go in between them.
You can use multiple <br> elements to push text down several lines, and many designers use two line breaks between paragraphs of text rather than using the <p> element to structure text, as follows:
Paragraph one<br><br> Paragraph two<br><br> Paragraph three<br><br>
Although two <br> elements look similar to using a <p> element, remember that HTML markup is supposed to describe the structure of the content. So if you use two <br> elements between paragraphs, you are not describing the document structure.
Here you can see an example of the <br> element in use within a paragraph (ch01_eg07.html):
<p>When you want to start a new line you can use the line break element. So, the next<br />word will appear on a new line.</p>
Figure 1-9 shows you how the line breaks look after the words “next” and “do.”
Figure 1-9
The <br> element can carry the following attributes:
class id style title
Creating Preformatted Text Using the <pre> Element
Sometimes you want your text to follow the exact format of how it is written in the HTML document; you don’t want the text to wrap onto a new line when it reaches the edge of the browser. You also don’t want it to ignore multiple spaces, and you want the line breaks where you put them.
Any text between the opening <pre> tag and the closing </pre> tag preserves the formatting of the source document. You should be aware, however, that most browsers display this text in a monospaced font by default. (Courier is an example of a monospaced font because each letter of the alphabet takes up the same width. Compare this to a nonmonospaced font, where an i is usually narrower than an m.)
The most common uses of the <pre> element are to represent computer source code. For example, the following shows some JavaScript inside a <pre> element (ch01_eg08.html):
<pre> function testFunction( strText ){ console.log( strText ) } </pre>
Figure 1-10 shows how the content of the <pre> element displays in the monospaced font. More important, you can see how it follows the formatting shown inside the <pre> element—the white space is preserved.
Figure 1-10
Although tab characters can have an effect inside a <pre> element, and a tab is supposed to represent eight spaces, the implementation of tabs varies across browsers, so it is advisable to use spaces instead.
You will come across more elements that you can use to represent code in the next chapter, “Fine-tuning Your Text,” which covers the <code>, <kbd>, and <var> elements.
Figure 1-11
Understanding Block and Inline Elements
Now that you have seen many of the elements that you can use to mark up text, you must consider all the elements that live inside the <body> element because each can fall into one of two categories:
Block-level elements
Inline elements
This is quite a conceptual distinction, but it has important ramifications for other features of HTML.
Block-level elements appear on the screen as if they have a carriage return or line break before and after them. For example, the <p>, <h1>, <h2>, <h3>, <h4>, <h5>, <h6>, <ul>, <ol>, <dl>, <pre>, <hr />, <blockquote>, and <address> elements are all block-level elements. They all start on their own new lines, and anything that follows them appears on its own new line, too.
Inline elements, on the other hand, can appear within sentences and do not need to appear on new lines of their own. The <b>, <i>, <u>, <em>, <strong>, <sup>, <sub>, <small>, <ins>, <del>, <code>, <cite>, <dfn>, <kbd>, and <var> elements are all inline elements.
For example, look at the following heading and paragraph; both of these elements start on new lines, and anything that follows them goes on a new line, too. Meanwhile, the inline elements in the paragraph are not placed on their own new lines. Here is the code (ch01_eg09.html):
<h1>Block-Level Elements</h1> <p><strong>Block-level elements</strong> always start on a new line. The <code><h1></code> and <code><p></code> elements will not sit on the same line, whereas the inline elements flow with the rest of the text.</p>
You can see what this looks like in Figure 1-12.
Figure 1-12
Strictly speaking, inline elements may not contain block-level elements and can appear only within block-level elements. (So you should not have a <b> element outside a block-level element.) Block-level elements, meanwhile, can contain other block-level elements and inline elements.
Grouping Content
You can find one of the most interesting new additions to the HTML5 specification in a number of new elements added to aid in grouping content. As you just learned, elements represent the different parts of an article with different levels of headings and paragraphs. As you’ll learn throughout the chapter, there are many other elements left to mark up to describe text.
One thing that was lacking was the ability to group all that well-described content into meaningful ways. So, although you could write an article and mark up each paragraph meaningfully, it wasn’t possible to indicate that the entire block of text was an article. HTML5 changes that with the addition of several new elements designed to enable you to more accurately group content.
This section introduces the various ways to group content in HTML.
The New Outline Algorithm in HTML5
In adding these new grouping elements, the authors of the specification made a change to the way headings are used in HTML. Before HTML5, the general standard was to have one <h1> element per page. The basic idea was that the entire HTML document was by itself a standalone element and should therefore have just one overall outline with a single <h1> at the top of the tree.
As the web evolved to contain more complicated, compound documents, this concept no longer held true for many of the documents on the web. With a blog, you can easily have several separate articles all contained in a single HTML document. Each of those articles could contain a logical outline of its own, independent of the rest of the page. Because of this, the ability to add more than one <h1> to the page inside different sectioning elements was added.
As you’ll learn throughout this section and as you continue to work with HTML5, there’s much greater flexibility in the ways you can structure pages using the new markup.
As an aid to work with HTML5 documents, there’s a handy bookmarklet and Google Chrome extension called the HTML5 Outliner (h5o) that can help to analyze the structure of your pages. Even experienced authors find it useful, so it’s definitely good to have on hand to make sure your pages make sense at the outline level. You can download it from Google code: http://code.google.com/p/h5o/.
The <div> Element
Before the extension of the grouping elements in HTML5, the most common container for groups of HTML elements was the <div>. It represents a generic block of content and is designed to be used with classes and ids to give structure to documents. Taking the markup from Example Café, you could mark it up with <div> elements representing different content sections.
For example, if you want to set the header apart in some way, you can mark it up like the following example. Using a <div> with a class of header you can encapsulate the site title and tagline into a single structure:
<div class="header"> <h1>EXAMPLE CAFE</h1> <p>Welcome to example cafe. We will be developing this site throughout the book.</p> </div>
Although this is actually quite useful for styling and scripting, there’s no semantic meaning behind the <div>, no matter how well chosen the classes or ids are. As you see throughout this section, the new sectioning elements in HTML5 enhance the utility of the <div>with (mostly) straightforward semantic meaning.
The <header> Element
As part of the development of the new specification, the editor of the HTML standard, Ian Hickson, did a survey of the web and identified common markup patterns. Some of these he captured as new HTML elements. This is one such element.
As you saw in the previous example, the concept of a “header” for common introductory or navigation content is a useful one and was repeated over and over on the web. Marking up the previous example with a <header> simplifies the markup and imparts more semantic meaning to the page.
<header> <h1>EXAMPLE CAFE</h1> <p>Welcome to example cafe. We will be developing this site throughout the book.</p> </header>
Although this example shows a header generated at the page level, you can also use headers within other grouping elements. For example, an <article> element, which you’ll learn about shortly, can have its own header containing information about the author, the data published, and the title of the article.
The <hgroup> Element
The <hgroup> element is designed to group together multiple levels of headings that have some logical connection, for example, subheadings, alternative titles, or taglines.
Adding an <hgroup> element, and a silly tagline, to the previous example illustrates how to use the <hgroup> element:
<header> <hgroup> <h1>EXAMPLE CAFE</h1> <h2>Serving Home Style Example Markup since 2012</h2> </hgroup> </header>
The <nav> Element
The <nav> element represents a navigation section of the page, containing a list of links to other pages or site sections within the site or application. Because the Example Café site is going to have more than one page, look at one way to mark up a simple menu linking to other pages on the site. In this example you can see a series of <p> tags, containing links to the site’s other pages. Later you learn about working with lists and learn a more common pattern for marking up navigational elements. For now, just focus on the use of the <nav> element.
<nav> <p><a href="recipes.html">Recipes</p> <p><a href="menu.html">Menu</a></p> <p><a href="opening_times.html">Opening Times</a></p> <p><a href-"contact.html">Contact</a></p> </nav>
The <section> Element
The <section> element is used to represent a section of a document or application. A <section> differs from a <div>, the most generic content grouping element, by the idea that content contained in a <section> is designed to be part of the document’s outline.
Although the Example Café site is going to have separate pages, it can conceivably be one page broken into several sections. A simplified example, just using the headings for each section and no content, would look something like this:
<section> <h1>Introduction</h1> </section> <section> <h1>Recipes</h1> </section> <section> <h1>Menu</h1> </section> <section> <h1>Opening Times</h1> </section> <section> <h1>Contact</h1> </section>
The <article> Element
In the words of the specification, you can use an <article> element to mark up “independent content.” That’s not the friendliest description, so it’s useful to think of common examples such as a blog post, a forum post, a movie review, a news article, or an interactive widget. The basic rule of thumb is that if the content can be syndicated or shared without the rest of the site context, it should be marked up as an article. For example, a short, glowing review of the Example Café might be marked up like the following example:
<article> <h1>Example Cafe, Great Food Delivered with Superior Markup and Style</h1> <p>It's rare to find a restaurant that combines as many exemplary elements as the example café. From the superior markup of the café's website to the delicious dishes served with care nothing about the Example Café is left to chance.</p> </article>
The <hr> Element
The <hr>
