Input Assistance: When users are entering input into the website, any input errors are automatically detected and written out, providing, for instance, text descriptions that identify fields that were not filled out or data that was in the wrong format. The website also provides suggestions to fix the errors. Input fields and buttons are labeled to provide their functions and instructions. If the user’s input is being used for legal purposes or financial transactions, then the user must be able to reverse submissions or correct errors.

"III-3.6000 Retaliation or coercion. Individuals who exercise their rights under the ADA, or assist others in exercising their rights, are protected from retaliation. The prohibition against retaliation or coercion applies broadly to any individual or entity that seeks to prevent an individual from exercising his or her rights or to retaliate against him or her for having exercised those rights ... Any form of retaliation or coercion, including threats, intimidation, or interference, is prohibited if it is intended to interfere."
As of 2015 the ADA had improved access to public services, the built environment (e.g., crosswalks with curb cuts and accessible pedestrian signals), understanding of the abilities of people with disabilities, established a right to equal access to public services and has demonstrated the contributions which people with disabilities can make to the economy. Disparities have remained in employment, earned income, Internet access, transportation, housing, and educational attainment and the disabled remain at a disadvantage with respect to health and health care.[45]

Federal law isn't the only consideration for businesses. Additionally, each state interprets the law differently. Consider the case against Netflix in 2012. Lawsuits were brought in federal court in Massachusetts and California. Netflix was accused of violating the ADA by not offering "closed captioning" options for its Internet streamed movies. Illustrating the complexity of this issue, the courts reached completely opposite decisions. Massachusetts held that Netflix must comply with the ADA, while the California court found that Netflix did not fall under the ADA's definition of "public accommodation."
In recent cases, the U.S. Department of Justice has repeatedly sided with plaintiffs arguing that a private company’s website needs to be accessible, despite any other mitigating factors. One thing is for certain, however: The number of federal lawsuits alleging violations of the ADA is currently accelerating at a rapid pace. Between January and August 2017, there were 432 ADA lawsuits filed in federal court—more than the total number of ADA lawsuits in 2015 and 2016 combined.

“The idea of equal access, equal opportunity has sort of evolved in its application from brick and mortar to eCommerce. At first, many companies were worried about the desktop experience. Now, the concern extends to both smart phones and devices.  Wherever a consumer accesses your content – whether it be directly through the web or an app – you need to be concerned about accessibility.”
State and local governments will often post documents on their websites using Portable Document Format (PDF). But PDF documents, or those in other image based formats, are often not accessible to blind people who use screen readers and people with low vision who use text enlargement programs or different color and font settings to read computer displays.
Leading web developers have been pioneering accessibility and publishing standards since 1994. In 1999, the Web Accessibility Initiative (WAI) and the World Wide Web Consortium (W3C) created the Web Content Accessibility Guidelines (WCAG). In essence, the people who determine how the internet is written came together to advise web developers on how to make websites accessible not only to people with disabilities, but to all web users, including those with highly limited devices.

On September 25, 2008, President George W. Bush signed the ADA Amendments Act of 2008 (ADAAA) into law. The amendment broadened the definition of "disability", thereby extending the ADA's protections to a greater number of people.[43] The ADAAA also added to the ADA examples of "major life activities" including, but not limited to, "caring for oneself, performing manual tasks, seeing, hearing, eating, sleeping, walking, standing, lifting, bending, speaking, breathing, learning, reading, concentrating, thinking, communicating, and working" as well as the operation of several specified major bodily functions.[43] The act overturned a 1999 US Supreme Court case that held that an employee was not disabled if the impairment could be corrected by mitigating measures; it specifically provides that such impairment must be determined without considering such ameliorative measures. It also overturned the court restriction that an impairment which substantially limits one major life activity must also limit others to be considered a disability.[43] In 2008, the United States House Committee on Education and Labor stated that the amendment "makes it absolutely clear that the ADA is intended to provide broad coverage to protect anyone who faces discrimination on the basis of disability."[44] Thus the ADAAA led to broader coverage of impaired employees.
This is an article that most other website developers probably don’t want you to read. The reason is that most other web designers basically like to think of themselves as all-powerful wizards with magical powers. And they use complex technical jargon and terminology to intimidate and mystify their clients into thinking that what they do is more complex than it is.

While legal considerations might be your biggest worry, making your site more accessible is simply good customer service. More than 39 million Americans are blind and another 246 million have "low vision," Another one million are deaf in the U.S. Add to that people with mobility issues that prevent them from using their hands and that's a huge portion of the country's buying power.