Website Accessibility

Disabled users

Blind users

Web users who have no sight at all may utilize a screen reader, which reads the content of the web page, or rather the HTML, back to them. This software, which sits between the user and the browser, sifts through the HTML markup and the technology deciphers what needs to be read aloud and what should be ignored.

Partial/poor sight

To take full advantage of the Internet, users with partial or poor sight typically use built in browser tools for increasing and decreasing the size of the website:

  • Click the “View” menu on the Web browser, click “Zoom” and then click “Zoom In” to increase the size of the Web page on Internet Explorer and Mozilla Firefox. To decrease the size of the page, click “Zoom” and then click “Zoom Out.” On Safari browser, click the “View” menu and then either click “Zoom In” or “Zoom Out” to increase or decrease the size of the page.
  • Press the “Ctrl” button and then the “+” button on your keyboard in combination while keeping the page in view to increase the page size. To decrease the size of the page, press the “Ctrl” and “-” buttons in combination.
  • Press and hold the “Ctrl” button and then roll the wheel on your mouse forward to increase the size of the page and backward to decrease the size.

Color blindness

It is estimated that one in 12 men and one in 200 women have some form of color blindness. You can check how Internet users with different strains of color blindness are viewing your website with Vischeck.

Deaf users

Deaf users are able to access the Internet in much the same way as non-deaf people with one key exception — audio content. If it’s a key function of your website for people to be able to hear a message, then be sure to provide written transcripts at the very least.

Keyboard/voice only users

Some of your site users don’t have access to a mouse when browsing the Internet. Try putting yourself in their position by navigating your website using only tab, shift-tab, and the return keys.

Other users

Other people who may access your website that have disadvantages include:

  1. Epileptic users who must always be careful to avoid seeing flickering between 2 and 55 Hz
  2. Web users from outside your industry who may not understand industry jargon or acronyms
  3. Web users whose first language is not English and who may not be able to comprehend complicated language

And finally …

Any web developer with basic HTML and CSS design knowledge, and a bit of time on their hands, can easily learn and implement web accessibility — it’s not brain science after all. Web accessibility is all about following design standards and then adding in a few simple accessibility features. It’s not just about disabled users being able to access your website — it’s about everyone being able to access your website.


HERA is a tool to check the accessibility of Web pages according to the specification Web Content Accessibility Guidelines. HERA performs a preliminary set of tests on the page and identifies any automatically detectable errors or checkpoints met, and which checkpoints need further manual verification. Manual revision is always needed to test whether a page is accessible. To be able to do this testing it is normally necessary to know the Accessibility Guidelines, how users work with assistive technology, and have some practical understanding of web page design. HERA assists in manual revision by highlighting the parts of the page that need checking, providing instructions on how to perform the tests, and offering two views of the page(normal page rendering and the HTML source code) with the most important elements for checking highlighted through colors and icons.

Readability Tests

Gunning Fog, Flesch Reading Ease, and Flesch-Kincaid are reading level algorithms that can be helpful in determining how readable your content is. Reading level algorithms only provide a rough guide, as they tend to reward short sentences made up of short words. Whilst they’re rough guides, they can give a useful indication as to whether you’ve pitched your content at the right level for your intended audience.

Color Blindness

Coblis – Color Blindness Simulator which will show you what various types of color blindness look like. There are also tests to check your level of color blindness!

Vischeck is a computer simulation of the entire process of human vision. The model can be divided into three parts:

  • The first stage includes the physical properties of the display devices (including various CRT and LCD monitors, and standard CYMK print on paper), the ambient lighting and the effects of physiological factors such as corneal haze, lens opacities and short or long-sightedness which might degrade the optical image.
  • The second stage of the model describes the transformation of optical image on the retina into a neural representation of that image in the optic nerve. At this point, visual disabilities and anomalies such as color-blindness or retinal degeneration can be included in the model.
  • The final stage in Vischeck is a model of human cortical vision. At this stage, we include information about the way in which color, spatial patterns and motion are combined and processed in the visual cortex, to form the observer’s perception of the image.

Cynthia Says

he Cryptzone Cynthia Says portal is a joint education and outreach project of Cryptzone, ICDRI, and the Internet Society Disability and Special Needs Chapter. Cynthia Says educates users in the concepts behind website accessibility. It is meant for personal, non-commercial use to inform the community on what constitutes accessible web design and content. It helps users identify errors in their Web content related to Section 508 standards and/or the WCAG guidelines for Web accessibility. Cynthia Says allows users to test individual pages on their website and provides feedback in a reporting format that is clear and easy to understand.

Readability Results

The following table contains the readability results for

Reading Level Results
Summary Value
Total sentences 876
Total words 2898
Average words per Sentence 3.31
Words with 1 Syllable 1476
Words with 2 Syllables 595
Words with 3 Syllables 345
Words with 4 or more Syllables 482
Percentage of word with three or more syllables 28.54%
Average Syllables per Word 1.94
Gunning Fog Index 12.74
Flesch Reading Ease 39.15
Flesch-Kincaid Grade 8.62

Gunning-Fog Index

The following is the algorithm to determine the Gunning-Fog index.

  • Calculate the average number of words you use per sentence.
  • Calculate the percentage of difficult words in the sample (words with three or more syllables).
  • Add the totals together, and multiply the sum by 0.4.
  • Algorithm: (average_words_sentence + number_words_three_syllables_plus) * 0.4

The result is your Gunning-Fog index, which is a rough measure of how many years of schooling it would take someone to understand the content. The lower the number, the more understandable the content will be to your visitors. Results over seventeen are reported as seventeen, where seventeen is considered post-graduate level.

Flesch Reading Ease

The following is the algorithm to determine the Flesch Reading Ease.

  • Calculate the average number of words you use per sentence.
  • Calculate the average number of syllables per word.
  • Multiply the average number of syllables per word multiplied by 84.6 and subtract it from the average number of words multiplied by 1.015.
  • Subtract the result from 206.835.
  • Algorithm: 206.835 – (1.015 * average_words_sentence) – (84.6 * average_syllables_word)

The result is an index number that rates the text on a 100-point scale. The higher the score, the easier it is to understand the document. Authors are encouraged to aim for a score of approximately 60 to 70.

Flesch-Kincaid grade level

The following is the algorithm to determine the Flesch-Kincaid grade level.

  • Calculate the average number of words you use per sentence.
  • Calculate the average number of syllables per word.
  • Multiply the average number of words by 0.39 and add it to the average number of syllables per word multiplied by 11.8.
  • Subtract 15.50 from the result.
  • Algorithm: (0.39 * average_words_sentence) + (11.8 * average_syllables_word) – 15.9

The result is the Flesch-Kincaid grade level. Like the Gunning-Fog index, it is a rough measure of how many years of schooling it would take someone to understand the content. Negative results are reported as zero, and numbers over twelve are reported as twelve.

Reading Level Algorithms

Readability is the measure of how easy it is to read and comprehend a document. Readability tests were first developed in the 1920s in the United States. They are mathematical formulas, designed to determine the suitability of books for American students at a certain age, or grade level. Automating the process was intended to make it easier for tutors, librarians, and publishers to determine whether a book would be suitable for its intended audience. The formulas are based around the average words to a sentence, and the average syllables used per word. As such, they tend to reward short sentences made up of short words. Being mathematically based, readability tests are unable to determine the likelihood that the document is comprehensible, interesting, or enjoyable. It’s possible to obtain good readability scores with gobbledygook, providing the content contains short sentences made up of monosyllabic words. We’ll leave the question as to why the word “monosyllabic” has five syllables for another day. Layout and design are also important factors to the readability of a document that cannot be determined using readability tests. Documents aimed at a higher level may require background knowledge, which cannot be determined by the tests. For a document to be easily understood, the writing style should be clear and simple. This involves a writing style that is direct, and familiar to the intended reader. The structure of the document should be logical, unambiguous, and avoid redundant words. Many of these factors cannot be measured using readability tests. Instead, readability tests provide a prediction of the reading ease for a document. Sentence length and polysyllabic words do have a direct impact on the readability of documents, albeit a surface measure of the characteristics of the text. They provide an indication that the content may be too dense with a quantifiable measure. The results should be used in conjunction with good writing style guidelines. Guideline 14 of the Web Content Accessibility Guidelines requires that documents are clear and simple. Readability tests can provide a rough guide to the likelihood of a document being clearly understood. This service is to provide content authors with a guide to the readability of their website.

Browser Shots

View a website at various screen sizes:




Learn everything from basic web accessibility principles to advanced accessibility techniques, and what you need to know to ensure that your web site meets legal guidelines and international standards.


  • How do individuals with disabilities interact with and use the web?
  • Understanding how assistive technologies work.
  • Understanding your legal requirements – Section 508, Section 504, the Americans with Disabilities Act, and other state, and U.S. laws.
  • Evaluating web site accessibility – automated tools, user testing, using screen readers, and understanding the Web Content Accessibility Guidelines (WCAG) 2.1.
  • Captioning considerations and recommendations
  • Images and appropriate alt text
  • Keyboard accessibility techniques
  • Evaluation tools, techniques, and methodologies
  • Accessible navigation, structure, and semantics
  • Document Accessibility – Adobe Acrobat (PDF) and Microsoft Office (Word and PowerPoint).

Training and Conferences

The following conferences and training programs address web and document accessibility. Any of these events would be valuable to web leaders, content creators, and site developers at Stanford.

Training Sites and Materials

For a quick hands-on, try the Teach Access tutorial.

There are two sites that offer “before and after” scenarios, so, if you already know a bit about accessibility, you can visit these sites to test your knowledge:

The Web Accessibility Initiative (WAI), part of the World Wide Web Consortium (W3C), has developed a “Before and After Demonstration.” Start with the Before and After Demonstration Overview.

The Accessible University overview page explains that you can see a “mock” inaccessible site, a site where the issues have been fixed, and a third page that lists the problems that visitors with disabilities would encounter.

You’ll be able to see code and explanations so you can learn how and why changes were made. Use your imagination, put yourself in the shoes of a range of site visitors with different access needs, and have fun!

If you have opportunities to develop web accessibility training materials for your colleagues, WAI provides a suite of training documents that includes course outlines for workshops of various lengths. Consulting Developing Web Accessibility Presentations and Training can save a good deal of preparation time.

Here are some examples of training available from third-party vendors. Some training (such as one-hour webinars) is free, though you typically have to register in advance. Other training may require a subscription, or a one-time payment, and sometimes, training is tied to a particular vendor’s product. Please make your selections with care, and take advantage of, or organize, group training opportunities whenever possible.

To learn more about Deque, visit:

SSB Bart Group’s offerings include:

Accessibility-Related Courses on

Members of the Stanford community have access to courses free of charge, using a SUNet id to login. Read more about how this excellent service works by visiting:

Since new Lynda courses are launched regularly, what is included here is a snapshot in time. If you have recommendations for additions, or updates, please Contact us.

Consider bookmarking Learn Accessibility with Video Courses and Tutorials from Perhaps this listing will grow, and you may find visiting the page on becomes the most up-to-date source on this subject.

Here are several courses with an accessibility-specific focus:

Other courses touch on accessibility, while covering general concepts:


Accessing Higher Ground (Accessible Media, Web and Technology Conference)
This Higher Ed focussed conference is typically held in min-November in Colorado. Topics covered include production of alternate media, legal and policy issues, instructional material and web accessibility training
CSUN Annual International Technology and Persons with Disabilities Conference
Hosted around March in southern California, this is the largest conference that covers web and document accessibility, a range of assistive technologies, policy development, etc. The conference usually has approximately 4,000 attendees. There are often hands-on preconference workshops that offer web accessibility training. Some main conference presentation videos are posted, but there is no formal virtual track.
WebAIM Two-day Training
This intensive training course is held a few times per year in Logan, Utah. Sometimes, it focuses on basic training, while sometimes, the course covers advanced accessibility techniques. The site provides a course outline. Check the site for current dates.
Knowbility’s John Slatin AccessU
AssessU is a training conference in Austin, TX. It has a wide-variety of classes, and often has virtual track options.
ICT Accessibility Testing Symposium
For practitioners of accessibility testing, you can find evaluation methods and strategies at this peer-reviewed symposium.
M-Enabling Summit
A Washington, DC conference dedicated to promoting mobile accessible and assistive applications and services for senior citizens and users of all abilities.
This research focussed Special Interest Group of ACM, SIGACCESS, promotes the interests of professionals working on research and development of computing and information technology to help persons with disabilities.

Accessibility Training for Developers

From general training to certification programs, there are many training options to help you improve your accessibility skills. Learn how to build digital tools that conform to the Revised 508 Standards.

General Training

Visit the Training page for general training on Section 508 and IT Accessibility.


The International Association of Accessibility Professionals (IAAP) offers two accessibility certifications:

Prepare for the IAAP certifications:

If you complete both certifications above, you’ll also receive a Certified Professional in Web Accessibility (CPWA) designation.

Education Initiatives

  • Teach Access – Aims to expand the quality and quantity of undergraduate programs that teach accessibility fundamentals in fields such as design, computer science, and human computer interaction

Web Accessibility Training

These resources (including some no-cost offerings) can help you understand how accessibility is achieved in certain specialized environments. You must understand your development environment to determine what, specifically, you’ll need to know.

Original 508 Standards

A number of organizations offer training based on the Original 508 Standards. Though the Standards have been revised, many are still valuable, including:

Web Accessibility

More modern resources include:

Topics for Web Accessibility Presentations and Training