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Web Accessibility Principles
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Proper ALT text for decorative images


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Web Accessibility Principles

with Zoe Gillenwater

Video: Proper ALT text for decorative images

>> In the last movie we talked about how important it is to use alt text that conveys the purpose of information than an image is providing. But there are some times when it can actually harm accessibility to add alt text to our images. Note that the section 508 with WCAG guidelines just require a text equivalent, that text equivalent doesn't have to be inside the image itself. The point is to make sure that screen reader users get all of the information sighted users do. So if the information the image conveys is also conveyed in the test else where on the page you met the requirement.
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  1. 2m 0s
    1. Welcome
      1m 3s
    2. Using the exercise files
      57s
  2. 33m 15s
    1. What does accessibility mean?
      5m 51s
    2. How does accessibility help your users?
      3m 30s
    3. Experiencing a website via a screen reader
      5m 46s
    4. How does accessibility help you and your clients?
      3m 9s
    5. Overview of Section 508 standards
      5m 51s
    6. Overview of WCAG standards
      6m 4s
    7. Understanding consistency and semantic markup
      3m 4s
  3. 54m 31s
    1. Understanding screen readers and accessibility tools
      6m 12s
    2. Getting accessible browsers
      5m 41s
    3. Customizing Firefox for accessibility testing
      5m 53s
    4. Using custom accessibility toolbars
      5m 28s
    5. Using Fangs and the Color Contrast Analyzer
      5m 30s
    6. Accessibility tools to bookmark
      5m 53s
    7. Using automated accessibility checking tools
      4m 57s
    8. Setting up the JAWS screen reader on Windows
      6m 42s
    9. Using the VoiceOver screen reader on Mac OS X
      5m 52s
    10. Setting Dreamweaver accessibility preferences
      2m 23s
  4. 26m 12s
    1. Avoiding tables for layout
      3m 30s
    2. Using CSS for layout
      2m 40s
    3. Creating a fixed-width layout
      5m 51s
    4. Creating an elastic layout
      3m 51s
    5. Creating a liquid layout
      3m 4s
    6. Customizing a liquid layout
      7m 16s
  5. 1h 6m
    1. Specifying the language
      3m 43s
    2. Setting page titles
      2m 16s
    3. Setting headings and paragraphs
      9m 55s
    4. Styling headings
      9m 56s
    5. Hiding section headings from sighted users
      6m 41s
    6. Styling text for readability
      6m 41s
    7. Ensuring proper color contrast
      6m 36s
    8. Creating text emphasis
      4m 29s
    9. Indicating quotations
      4m 29s
    10. Creating basic lists
      4m 16s
    11. Styling lists
      7m 15s
  6. 1h 15m
    1. Using lists for navigation
      6m 45s
    2. Creating a horizontal navigation bar
      13m 25s
    3. Creating a vertical navigation bar
      11m 44s
    4. Adding skip navigation links
      12m 0s
    5. Hiding skip navigation links
      6m 17s
    6. Proper link text and title attributes
      6m 11s
    7. Opening new windows
      4m 28s
    8. Accessibility limitations of fly-out menus
      6m 30s
    9. Creating an accessible fly-out menu
      8m 38s
  7. 27m 55s
    1. Proper ALT text for navigation images
      4m 57s
    2. Proper ALT text for decorative images
      5m 19s
    3. Adding ALT text to an existing site
      6m 9s
    4. Adding ALT text to image maps
      5m 58s
    5. Describing complex graphics
      5m 32s
  8. 34m 1s
    1. Using tables for data
      3m 0s
    2. Creating header cells
      4m 5s
    3. Adding table captions and summaries
      9m 9s
    4. Styling tables
      5m 19s
    5. Applying header cells to complex tables
      6m 52s
    6. Adding id and headers attributes
      5m 36s
  9. 42m 7s
    1. Understanding form accessibility issues
      3m 7s
    2. Labeling form fields
      6m 9s
    3. Adding fieldsets and legends
      4m 42s
    4. Moving forms out of tables
      3m 44s
    5. Cleaning up a form's appearance
      4m 53s
    6. Aligning labels and fields using CSS
      9m 39s
    7. Indicating required fields
      6m 15s
    8. Dealing with CAPTCHA
      3m 38s
  10. 7m 29s
    1. The Text-Only technique
      3m 21s
    2. The Access Keys technique
      2m 35s
    3. The Tab Index technique
      1m 33s
  11. 18s
    1. Goodbye
      18s

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Web Accessibility Principles
6h 10m Appropriate for all Oct 16, 2007

Viewers: in countries Watching now:

Accessibility on the web has been an issue for over a decade, and it remains a crucial--but often overlooked--element of web design. Instructor Zoe Gillenwater explains the concept of accessibility as it applies to the web, and describes how it affects the audience. She also covers how to set up accessibility testing, and how to apply accessibility principles to new and existing sites using standards-compliant markup and CSS. Exercise files accompany the tutorials.

Topics include:
  • Understanding Flex programming languages
Subjects:
Web User Experience Accessibility
Author:
Zoe Gillenwater

Proper ALT text for decorative images

>> In the last movie we talked about how important it is to use alt text that conveys the purpose of information than an image is providing. But there are some times when it can actually harm accessibility to add alt text to our images. Note that the section 508 with WCAG guidelines just require a text equivalent, that text equivalent doesn't have to be inside the image itself. The point is to make sure that screen reader users get all of the information sighted users do. So if the information the image conveys is also conveyed in the test else where on the page you met the requirement.

If you were to repeat the equivalent in an alt attribute the screen reader user would have to hear it twice which is unnecessary and would probably be very frustrating. Let's look at an example. If you are following along with the exercise files open residents.html in Dreamweaver, it is located in the 0602 folder of the chapter six exercise files. Scroll down the page to see the entire image, underneath the image is written the caption.

This is simply a regular paragraph element but note that it's providing information about the image. In this case the text equivalent is provided in this paragraph. There is no need for us to repeat it inside the alt attribute image itself. But the screen reader still needs to be told that the image already has a text equivalent else where on the page. This is done by including the alt attribute on the image but leaving it value blank. The screen read has nothing to read so it just skips over the image which is exactly what we want.

Click on the photograph, you'll see on the alt field of the properties inspector that no value is currently set, that doesn't mean that the alt attribute has been set to empty as we want. Where there is no content inside the properties inspector in Dreamweaver it means that the alt attribute is missing from the image tag all together. So click on the arrow in the alt field and choose the option empty. When we choose this option Dreamweaver adds the alt attribute to the image that keeps it value empty.

Let's see this by going into the code view. Click on the code button in the document toolbar, the alt attribute is now in the image tag but there is not content between the quotation marks, this is exactly what we want to happen. Another scenario where you would want screen readers to skip over an image is if the image was purely decorative. In those cases it is really just there for the sake of sighted users and there is no text equivalent that you'd want a screen reader user to hear. So we would again use an empty alt attribute.

Open the page index.html from the same exercise files folder. We're going to add a decorative image to this page. In design view place your cursor at the start of the first paragraph of text, then go to the insert menu and choose image. In the select image source dialog box browse for the location of the exercise files on your computer, go to the chapter six folder and then the 0602 folder and then the images folder and chose the image named carnival.jpeg, click OK.

The image tag accessibility attributes dialog box appears. This dialog box comes up because earlier we set our Dreamweaver preferences to prompt us for accessibility on images, frames, media and forms. If we had the images accessibility preference unchecked we wouldn't see this field. We could still add alt text to all of our images of course but this serves for a good reminder to do so ever time we enter a new image. We want the alt attribute to be blank so click on the arrow in the alternate text menu and choose empty.

Don't worry about the long description field for right now, we will cover that in a later movie, click OK. The image is now added to the page, you can see in the properties inspector page that the alt attribute has been set to empty. Using empty alt attributes is especially important in old table based pages because they frequently us spacer GIFs or other images for formatting purposes. You would give these images empty alt attributes, never spacer images or anything along those lines. Other examples of decorative images would include images used for bullets or dividing lines.

This points to another advantage of CSS layouts, most of the decorative images are kept in the style sheet so there's no needs to worry about setting empty alt attributes on them, but for all of the images you have in HTML of the page an alt attribute should always be present on the tag. The content of that alt attribute will depend on whether that image is content, navigation or decoration and whether the content of the image is conveyed in text elsewhere on the page. If you have many old pages that you need to add alt text to our next movie will go over so ways to speed up that process.

There are currently no FAQs about Web Accessibility Principles.

 
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