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Design accessible web sites 36 Keys to Creating Content for All Audiences and Platforms

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Design accessible web sites 36 Keys to Creating Content for All Audiences and Platforms

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"Accessibility" has a reputation of being dull, dry, and unfriendly toward graphic design. But there is a better way: well-styled semantic markup that lets you provide the best possible results for all of your users. This book will help you provide images, video, Flash and PDF in an accessible way that looks great to your sighted users, but is still accessible to all users.

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Nội dung Text: Design accessible web sites 36 Keys to Creating Content for All Audiences and Platforms

  1. Thank you for taking part in this experiment. Andy and Dave
  2. Design Accessible Web Sites Thirty-Six Keys to Creating Content for All Audiences and Platform Jeremy J. Sydik The Pragmatic Bookshelf Raleigh, North Carolina Dallas, Texas
  3. Many of the designations used by manufacturers and sellers to distinguish their prod- ucts are claimed as trademarks. Where those designations appear in this book, and The Pragmatic Programmers, LLC was aware of a trademark claim, the designations have been printed in initial capital letters or in all capitals. The Pragmatic Starter Kit, The Pragmatic Programmer, Pragmatic Programming, Pragmatic Bookshelf and the linking g device are trademarks of The Pragmatic Programmers, LLC. Quotation from “The Hobbit” by J. R. R. Tolkien. Copyright © 1937, 1966 by The J. R. R. Tolkien Copyright Trust. Reprinted by permission of The J. R. R. Tolkien Copyright Trust. Quotation from “Monty Python and the Holy Grail.” Copyright © 1975 by Python (Monty) Pictures Ltd. Reprinted by permission of Python (Monty) Pictures Ltd. Web Content Accessibility Guidelines 1.0 (Recommendation) http://www.w3.org/TR/WCAG10/ Copyright © 1999 World Wide Web Consortium (Massachusetts Institute of Technology, European Research Consortium for Informatics and Mathematics, Keio University). All Rights Reserved Web Content Accessibility Guidelines 2.0 (Public Working Draft) http://www.w3.org/TR/WCAG20/ Copyright © 2007 World Wide Web Consortium (Massachusetts Institute of Technology, European Research Consortium for Informatics and Mathemat- ics, Keio University). All Rights Reserved Cover image courtesy of Katherine A.W. Sydik Every precaution was taken in the preparation of this book. However, the publisher assumes no responsibility for errors or omissions, or for damages that may result from the use of information (including program listings) contained herein. Our Pragmatic courses, workshops, and other products can help you and your team create better software and have more fun. For more information, as well as the latest Pragmatic titles, please visit us at http://www.pragmaticprogrammer.com Copyright © 2007 Jeremy J. Sydik. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmit- ted, in any form, or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior consent of the publisher. Printed in the United States of America. ISBN-10: 1-934356-02-6 ISBN-13: 978-1-934356-02-9
  4. Contents Acknowledgments 10 Preface 12 Getting to Know Each Other . . . . . . . . . . . . . . . . . . . 13 Finding Your Way Through This Book . . . . . . . . . . . . . . 14 Principles Before Guidelines . . . . . . . . . . . . . . . . . . . . 15 Part I—Laying the Foundation 18 Why Be Accessible? 19 1.1 It’s the Right Thing to Do . . . . . . . . . . . . . . . . . 19 1.2 Accessibility is Good Business . . . . . . . . . . . . . . 20 1.3 Accessible Sites are More Usable . . . . . . . . . . . . . 21 1.4 It’s the Law . . . . . . . . . . . . . . . . . . . . . . . . . 21 1.5 Building with Accessibility Can Make You More Capable 24 A Brief Introduction to Disabilities 26 2.1 Visual Impairments . . . . . . . . . . . . . . . . . . . . . 26 2.2 Auditory Impairments . . . . . . . . . . . . . . . . . . . 29 2.3 Mobility Impairments . . . . . . . . . . . . . . . . . . . 31 2.4 Cognitive Impairments . . . . . . . . . . . . . . . . . . . 32 2.5 Multiple Disabilities . . . . . . . . . . . . . . . . . . . . 33 An Environment for Access 35 1. Making a Team Effort . . . . . . . . . . . . . . . . . . . 37 2. Plan for Access . . . . . . . . . . . . . . . . . . . . . . . 46 3. Multiple Access Paths . . . . . . . . . . . . . . . . . . . 53 4. Don’t Get WET! . . . . . . . . . . . . . . . . . . . . . . . 57 5. Guidelines for Accessibility . . . . . . . . . . . . . . . . 61
  5. C ONTENTS 7 Testing for Accessibility 64 6. Testing as a Design Decision . . . . . . . . . . . . . . . 65 7. Building a Testing Toolbox . . . . . . . . . . . . . . . . 69 8. Getting Your Hands Dirty . . . . . . . . . . . . . . . . . 76 Part II—Building a Solid Structure 81 The Structured Life 82 9. Say It With Meaning . . . . . . . . . . . . . . . . . . . . 83 10. Keeping It Simple is Smart . . . . . . . . . . . . . . . . 89 11. Minding Your ’s and ’s . . . . . . . . . . . . . . . 94 12. Linking It All Together . . . . . . . . . . . . . . . . . . . 98 13. Styled To The Nines . . . . . . . . . . . . . . . . . . . . 101 14. Welcome To The Future . . . . . . . . . . . . . . . . . . 105 Round Tables 110 15. Setting The Table . . . . . . . . . . . . . . . . . . . . . . 111 16. Ah, , I Hardly Knew Ye! . . . . . . . . . . . . . . 115 17. Layout And Other Bad Table Manners . . . . . . . . . . 122 The Accessible Interface 130 18. It’s Their Web—We’re Just Building In It . . . . . . . . 131 19. Getting al . . . . . . . . . . . . . . . . . . . . . . 135 20. Tickling The Keys . . . . . . . . . . . . . . . . . . . . . . 142 21. Your Interface Has Some Explaining To Do . . . . . . . 145 Part III—Getting the Perfect View 149 A Picture is Worth... 150 22. Stoplights and Poison Apples . . . . . . . . . . . . . . . 151 23. Thinking in Terms of Black and White . . . . . . . . . . 157 24. To Put it Another Way . . . . . . . . . . . . . . . . . . . 162 25. More Than alt= Can Say . . . . . . . . . . . . . . . . . . 167 26. alt.text.odds-and-ends . . . . . . . . . . . . . . . . . . . 174 Video Killed the Something-Something 179 27. It’s Not Polite to Flash the Audience . . . . . . . . . . . 181 28. Words That Go [Creak] in the Night . . . . . . . . . . . 185 29. Describe it to Me . . . . . . . . . . . . . . . . . . . . . . 190 30. On the Cutting Room Floor . . . . . . . . . . . . . . . . 194
  6. C ONTENTS 8 Part IV—Putting on Some Additions 206 Not All Documents Are Created Equal 207 31. Back at the Office . . . . . . . . . . . . . . . . . . . . . . 209 32. PDF: Trying to Make Portable Accessible . . . . . . . . 213 Scripted Responses 221 33. Unassuming Scripts . . . . . . . . . . . . . . . . . . . . 222 34. Higher Order Scripts . . . . . . . . . . . . . . . . . . . . 226 Embedded Applications: Rinse and Repeat 232 35. The Many Faces of Flash . . . . . . . . . . . . . . . . . 233 36. Java: Is Your Brew Fair-Trade? . . . . . . . . . . . . . . 239 Part V—Building Codes 243 Web Content Accessibility Guidelines 1.0 244 13.1 Checkpoint Priorities . . . . . . . . . . . . . . . . . . . . 245 13.2 Conformance . . . . . . . . . . . . . . . . . . . . . . . . 246 13.3 The 14 Guidelines of WCAG 1.0 . . . . . . . . . . . . . 247 Section 508 261 14.1 Software Applications and Operating Systems (§1194.21) 262 14.2 Web-Based Intranet and Internet Information and Applications (§1194.22) 264 14.3 Video and Multimedia Products (§1194.24) . . . . . . . 267 Web Content Accessibility Guidelines 2.0 270 15.1 The Basics of WCAG 2.0 . . . . . . . . . . . . . . . . . . 271 15.2 Concerns About WCAG 2.0 . . . . . . . . . . . . . . . . 272 15.3 The WCAG 2.0 Guidelines . . . . . . . . . . . . . . . . . 273 Meanwhile, In the Rest of the World... 288 16.1 Australia . . . . . . . ...... . . . . . . . . . . . . . . 289 16.2 Canada . . . . . . . . ...... . . . . . . . . . . . . . . 289 16.3 The European Union ...... . . . . . . . . . . . . . . 290 16.4 Japan . . . . . . . . . ...... . . . . . . . . . . . . . . 291 16.5 United Kingdom . . . ...... . . . . . . . . . . . . . . 292 16.6 United Nations . . . ...... . . . . . . . . . . . . . . 292 16.7 More Information . . ...... . . . . . . . . . . . . . . 294
  7. C ONTENTS 9 Final Thoughts 295 17.1 Keep Trying . . . . . . . . . . . . . . . . . . . . . . . . . 295 17.2 Stay Informed . . . . . . . . . . . . . . . . . . . . . . . . 295 17.3 Have Fun . . . . . . . . . . . . . . . . . . . . . . . . . . . 296 Bibliography 298 Index 299
  8. The Journey is the Reward. Zen Proverb Acknowledgments Every journey has a beginning and, in the case of this book, the journey truly began over ten years ago at the University of Nebraska—Lincoln Accommodation Resource Center. Dr. Christy Horn first showed me the importance of accessibility and has continued ever since to shape me as a professional and as a person. Thank you for your mentorship and your friendship. I also thank Christy, Roger Bruning, Barbara Robert- son and everyone else at the Center for Instructional Innovation for contributing to the supportive environment that makes working on a project like this possible. The road to this book would have been impossible to navigate without help along the way. Mike Hostetler, Peter Krantz, Jason Kunesh, Florian Ockhuysen, Aza Raskin, Ian Scheitle, and Warren Werner read early versions of this content, reviewed chapter drafts, and called me to task when I oversimplified or underexplained. This book is much better for your help (But I’m still taking credit for all of the mistakes, so there). Susannah Davidson Pfalzer had the (sometimes extremely) challenging task of being the development editor for this project. I know I’m not easy to negotiate with, so thank you for pushing when you knew this book could be better and for trusting my judgement when I was convinced that we were on the right path. I’d also like to thank Dave Thomas for listening to the original concept for this book at RailsConf 2006 and believing in the idea of a principles-based approach to web accessibility. Dave, along with Andy Hunt, also answered many of the questions that came up along the way about production, layout, copyright, and all of the other things that turn a bunch of words into a book. It has been an honor to write a Pragmatic Bookshelf title. To get where you’re going, you need to remember where you came from. My Mom and Dad are responsible for teaching me to believe in doing the right thing, helping people who need to be helped, and trying to be the best person I can be. (The rest is my own fault.) I’d also like to
  9. A CKNOWLEDGMENTS 11 thank Gerry, Susie, Stephen, Jeannine, my grandparents, and the rest of my family for their faith and prayers for this project and their under- standing when I sometimes nodded off on a couch at family gatherings. For every blessing that I have received, for giving me strength along this path, and for all things, I thank God. The difference between journeying and being lost is knowing where home is. I want to thank you Kate. You’ve been my editor, reviewer, cover designer, and first audience for this project. More importantly, you are the mother of my son, my girlfriend, my best friend and my wife. The things I do here and elsewhere are meaningless without that. Finally, I’d like to thank my son, Aidan. You’re young enough that you won’t remember much about your dad wandering around late at night muttering about chapters, edits, markup, and guidelines but my favorite part about late night writing was sitting with you long after your mom was asleep and sharing a snack after I was done for the evening. You remind me every morning why I want a better world and every evening that, with you in it, I’m already in a better world. Jeremy J. Sydik August, 2007
  10. New information and communications technologies can improve the quality of life for people with disabilities, but only if such technologies are designed from the beginning so that everyone can use them. Given the explosive growth in the use of the World Wide Web for publishing, electronic commerce, lifelong learning and the delivery of government services, it is vital that the Web be accessible to everyone. William Jefferson Clinton, Statement of Sup- port for the Web Accessibility Initiative Preface It was a dark and stormy night... Actually, It was a late summer afternoon a little over ten years ago when I first began to get accessibility. Back then, I was working as a student web developer and sysadmin and we needed a system for a blind user to work on a paper. Simple enough—we had some new systems. Just grab one, install it, add the specialized software and we’re done. I was fairly happy about the job—it was my first time through this kind of configuration and I finished with plenty of time so I added on nicer (I thought) speakers and keyboard. Our user came in and started to use the system—or at least tried to use the system. Everything started to fall apart. The keyboard was one of the newer (at the time) ergonomic keyboards, which the user had never worked with. The speakers were an even bigger problem. They came out of the box set to a low volume and I hadn’t thought to set them high so they could be controlled from software. The user’s began to panic when the interface to the system was completely disrupted. Two decisions that wouldn’t have usually been a problem turned the afternoon into a disaster. Of course, the real problem was human, not technological. My mis- take was in my assumption about how people use computers which, of course, was how I used a computer. I knew that blind users needed to use special software on their computers, but I didn’t consider the real difference in user experience. Later that evening, I got curious about my web sites—seeing how much difference something as simple as a different keyboard could make, how would my sites behave for users with screen readers instead of monitors and keyboards but not mice? It wasn’t pretty. I knew that I needed to design my sites differently, but what exactly did I need to do? It turns out that accessibility isn’t really that much about what you do—it’s a matter of how you do it. What
  11. G ETTING TO K NOW E ACH O THER 13 I really needed was information on what being accessible means and how to think from the perspectives of many kinds of users. Accessibility for the web is about designing content to be reachable by the largest number of users possible. There are a lot of ways to be acces- sible. Content can be accessible from a variety of hardware platforms or browsers. Accessibility can also be in terms of which technologies are assumed to be available to the user—less is more. Finally—and most importantly for us since it will be the primary focus of this book— content can be made accessible to users with disabilities. This kind of accessibility means tailoring our content to be useful for people with a wide range of physical, mental, and sensory abilities. As far as the other kinds of accessibility, we’ll get the best of both worlds. Content that is made accessible for users with disabilities is usually well on the way to being ready for multiple platforms and browsers as well. Getting to Know Each Other This book is about learning to apply accessibility principles to your web development practices. In other words, if you have anything to do with building web sites, there’s something here for you. You could be a project manager, a designer, a developer, an author, or an artist (Take a look at Making a Team Effort , on page 37 to see how different people fit into the accessibility process). I’ve written information that will be useful for anyone who wants to produce accessible web sites. You might want to do this because you believe it’s the right thing to do, because you know it’ll make your sites more portable to different platforms, or because you are concerned about the consequences of accessibility laws. These are all valid reasons and, for each of them, you’ll find plenty of useful principles and techniques here. I’m also going to assume, however, that you understand the basics of web development. We’ll be covering accessibility as it relates to HTML, CSS, images, video, and sound. We’ll also make brief excursions into accessibility for external document formats, JavaScript, Flash, and Java. We’re not going to be covering how to use these technologies beyond what we need for using them accessibly but I’ll do my best to point you toward plenty of good resources to check out if you feel like you need help getting up to speed. I think it’s important to mention, however, that I’m not a member of any of the committees you’ll read about in this book or the developer of any of the tools. When I give a recommen-
  12. F INDING Y OUR WAY T HROUGH T HIS B OOK 14 dation, it’s because I find the tool/book/website/whatever useful when I write pages. There are three things that I won’t be doing in this book, however. I won’t be spending a lot of time explaining (over and over and over) that accessibility is a good thing. I’m assuming that you’re already partly convinced if you’re reading this so we’ll take look a quick look at why accessibility is a good thing in Chapter 1, Why Be Accessible? , on page 19. After that, it’s down to business. I also won’t be ripping apart good visual design. Great visual design is an important element of the web and I welcome every designer who wants to add accessibility to their toolbox to come along—there’s plenty of information here for you as well. Finally, I’m not going to focus primarily on accessibility guidelines. I don’t think this is a useful route for understanding the principles that underlie web accessibility, so we’re going to take a prin- ciples first approach. We’ll get to the guidelines after we have a better understanding of what they mean. Finding Your Way Through This Book Web content is often referred to in terms of places like sites, home pages, stores, and so on. That works fine—if we’re building places, we can look at our users as visitors or, better yet, as guests. With that in mind, we’ll look at the concepts in this book in terms of building these places. I’ve laid out the concepts in this book in order from basic concepts to extra details: • Part I—Laying the Foundation : All good buildings start with a strong foundation. Here, we’ll get you started with a basic look at acces- sibility, why it’s important and how to get started with accessible development. • Part II—Building a Solid Structure : Like the framing of a building, markup gives our site a defined form. In this part, we’ll look at web semantics and understanding how to use markup and styles in an accessible way. • Part III—Getting the Perfect View: When a building is well designed, the views from it are remarkable, when it isn’t, the views are lack- ing. When we add accessibility features to our images, videos, and sounds, we provide the best view possible for our entire audience. In this part, we’ll learn how to add alternative information for accessibility.
  13. P RINCIPLES B EFORE G UIDELINES 15 • Part IV—Putting on Some Additions: We might want to put some extra features into our buildings. There are also extra things like external documents, scripts, and plug-in technologies that we can use in our sites that are at the edges of the web itself. In this part, we’ll look at applying accessibility principles to these as well. • Part V—Building Codes: Before a building is complete, it’s inspected. Web sites should also be checked for correctness and, in this part, we’ll wrap up by looking at the standards and how they connect to the things we’ve learned in the rest of the book. It’s not strictly necessary to follow the entire book in order, however. You should start with Chapter 1, Why Be Accessible? , on page 19 and Chap- ter 2, A Brief Introduction to Disabilities, on page 26 first but, after that, you should feel free to move in the order you find most useful. If you’re managing site development, you should probably continue into Chap- ter 3, An Environment for Access, on page 35 but, if you’re a graphic designer, you might find it more useful to jump ahead to Chapter 8, A Picture is Worth..., on page 150. Chapters three through twelve are comprised of a series of thirty-six tips. These tips are meant to stand on their own—you should be able to spend a short time with each tip, get the information you need and walk away to apply it to your own projects. The Act on It! sections are there to give you some ways to get started. Don’t just read these—give them a try! After you’ve been through the tips, go ahead and read through the dis- cussion of guidelines and laws in Part V. They’ll make a lot more sense once you’ve been through the rest of the book but, if they’re still confus- ing, my commentary will point you back to the part of the book where the underlying principle is covered. Principles Before Guidelines This book is going to take a principles before guidelines approach to accessibility. Staying focused on compliance issues is a common approach to accessibility, so it may seem surprising that I’m going to push the guidelines out of the way for now. Guidelines are useful for sorting out details and testing for compliance but they’re not written as instruc- tional documents. Our goal is helping as many of our users as possible get the information they want—not learning to be “rules lawyers” When we add video to our sites, we don’t want to be thinking:
  14. P RINCIPLES B EFORE G UIDELINES 16 “Section 508, §1194.24(c) says: All training and informational video and multimedia productions which support the agency’s mission, regardless of format, that contain speech or other audio information necessary for the comprehension of the content, shall be open or closed captioned” This places our priority on compliance instead of on our users. We really want think about it like this: “Ok, we’re using video. Which of our users does this affect? Well, for users who can’t see the video, we should add audio descriptions and we’ll add captions for people with hearing disabilities. Hmmm—Some of our users might not have the video player we’re asking for. We should also add a transcript of the video. Is there anyone else we might be miss- ing?” This approach is user focused and, at the end of the day, that’s what accessibility is all about. We’re going to follow ten rules when we design accessible sites: Ten Principles for Web Accessibility 1. Avoid making assumptions about the the physical, mental, and sensory abilities of your users whenever possible. 2. Your users’ technologies are capable of sending and receiving text. That’s about all you’ll ever be able to assume. 3. Users’ time and technology belong to them, not to us. You should never take control of either without a really good reason. 4. Provide good text alternatives for any non-text content. 5. Use widely available technologies to reach your audience. 6. Use clear language to communicate your message. 7. Make your sites usable, searchable, and navigable. 8. Design your content for semantic meaning and maintain separa- tion between content and presentation. 9. Progressively enhance your basic content by adding extra fea- tures. Allow it to degrade gracefully for users who can’t or don’t wish to use them. 10. As you encounter new web technologies, apply these same princi- ples when making them accessible.
  15. P RINCIPLES B EFORE G UIDELINES 17 These principles apply to just about everything you’ll need to do to design accessible sites. Of course, you’ll need to understand how to apply them. That’s good, because we’re just getting started.
  16. Part I Laying the Foundation
  17. Injustice anywhere is a threat to justice everywhere. Martin Luther King Jr., Letter from Birming- ham Jail, 1963.4.16 Chapter 1 Why Be Accessible? We’re going to spend a few hundred pages learning about web acces- sibility and how to apply the ten principles introduced in the preface. In this chapter, we’ll look at reasons why you should want to do this. There are plenty of good reasons to build accessible content. Some, like legal requirements, aren’t terribly pleasant to think about. Others, like opening your sites to new markets and increasing your skill set are more exciting to pursue. By the end of this chapter, you will be able to understand what your reasons for developing accessible web con- tent are. With that in mind, lets look at some benefits of understanding accessible web development. 1.1 It’s the Right Thing to Do While the web was originally designed for scientific communication, it was rapidly adopted as a new form of publishing with the promise to be wide-reaching and open to everyone. As web developers, we haven’t always lived up to this promise, however. As web technologies grew in complexity, many features appeared that threatened the openness of the web. In some cases, certain browsers were restricted from accessing content, in others multimedia was provided without alternative means of access. These changes have made the web less accessible over time. Shutting out users this way is entirely against the nature and intent of web communication. We should also keep in mind that accessibility to information and services is an issue of civil rights. The Universal Declaration of Human Rights1 states it best: “Everyone has the right Article 27.1 (http://www.un.org/Overview/rights.html ) 1.
  18. A CCESSIBILITY IS G OOD B USINESS 20 freely to participate in the cultural life of the community, to enjoy the arts and to share in scientific advancement and its benefits.” When we create accessible content, we help to realize this promise for our users. 1.2 Accessibility is Good Business The biggest advantage of developing content for the web is gaining access to an audience that was once beyond the wildest dreams of the largest publishers. If you create inaccessible content, you ignore part of this audience. Some developers write off this audience because they think the population in need of accessible web content is too small to consider. Just how small of a potential market are we talking about? Not so small at all, actually. Lets take a closer look. The Market of Users with Severe Disabilities In 2000, the United States census found that nearly one in eight people have a severe disability. Because accessible web content can be read with assistive technologies and is available from the home, people with disabilities can find information and make purchases with less hassle and inconvenience than by traveling to another location and seeking the assistance of others. This is really the same reason most of us use the web but, for persons with sensory or mobility disabilities that make it difficult to travel or communicate it is even more appealing. The bottom line is that 10 million people with severe disabilities represent a 46 billion dollar market that wants access to web based services. The Aging Population The reality of an aging population is beginning to make a huge dif- ference in the way we approach web development. Over the next two decades we will reach a point where one in five United States citizens will reach the age that vision, hearing, and mobility problems become more common. The baby boomer generation is used to having control over their consumer environment, and there is no reason to expect this to change as they reach retirement age. They will be expecting our sites to cater to their needs and they represent a large enough market that it would be unwise to disappoint them. The market for accessible web content and services is out there and growing. These are our potential readers and customers to the tune of 100 billion dollars a year—Why would we choose to ignore them?

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