Barden v. The City of Sacramento, filed in March 1999, claimed that the City of Sacramento failed to comply with the ADA when, while making public street improvements, it did not bring its sidewalks into compliance with the ADA. Certain issues were resolved in Federal Court. One issue, whether sidewalks were covered by the ADA, was appealed to the 9th Circuit Court of Appeals, which ruled that sidewalks were a "program" under ADA and must be made accessible to persons with disabilities. The ruling was later appealed to the U.S. Supreme Court, which refused to hear the case, letting stand the ruling of the 9th Circuit Court.[62][63]

Until the ADA is updated to address the special case of website accessibility, or the Department of Justice releases its website accessibility regulations, complying with WCAG 2.0 Level AA is the best way to ensure that people with disabilities have equal access to your website. The overview below is a great starting point about meeting the WCAG 2.0 Level AA recommendations.
Nice Article! It is very important to work under guidelines if you don’t want to get sued and don’t want to pay the penalties. But more importantly it is better to give each user hassle free user experience over your website. Being ADA Compliant means your website works well for people with disabilities and they can easily access and navigate your website.

This is the reason why I think web design firms have to position themselves as solution providers and not just web guys/gals. A client doesn't need a website, they need sales. The website is just part of that solution but it's not the solution and unlike web design, service like email marketing automation, SEO, and PPC requires an experienced professional.
While the U.S. Department of Labor's (DOL) Office of Disability Employment Policy (ODEP) does not enforce the ADA, it does offer publications and other technical assistance on the basic requirements of the law, including covered employers’ obligation to provide reasonable accommodations to qualified job applicants and employees with disabilities. For a quick overview of the ADA read “The Americans with Disabilities Act: A Brief Overview.”
You may file a charge of discrimination on the basis of disability by contacting any EEOC field office, located in cities throughout the United States. If you have been discriminated against, you are entitled to a remedy that will place you in the position you would have been in if the discrimination had never occurred. You may be entitled to hiring, promotion, reinstatement, back pay, or reasonable accommodation, including reassignment. You may also be entitled to attorneys fees.
Web designers often design in such a way that does not allow the user to adjust font size or color. While they may be protecting their brand, they are also inhibiting some users. Many visually impaired need to use high contrast color settings or very large fonts to read a website. Don't design your website in a way that makes it impossible for them to do this. 
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."
To be protected under the ADA, you must have, have a record of, or be regarded as having a substantial, as opposed to a minor, impairment. A substantial impairment is one that significantly limits or restricts a major life activity such as hearing, seeing, speaking, walking, breathing, performing manual tasks, caring for oneself, learning or working.
Another federal agency, the Architectural and Transportation Barriers Compliance Board (ATBCB), also known as the Access Board, issues guidelines to ensure that buildings, facilities and transit vehicles are accessible to people with disabilities. The Guidelines & Standards issued under the ADA and other laws establish design requirements for the construction and alteration of facilities. These standards apply to places of public accommodation, commercial facilities, and state and local government facilities.

The trick to finding top web designers is to understand what you’re trying to build. There’s a big difference between designing a landing page meant to be the receiving end of a sales funnel and building an enterprise site that will serve corporate clients. The web designer is responsible for translating your unique brand identity into the visual elements that make up a website. The cost of your project will depend largely on your scope of work and the specific skills needed to bring your project to life.

ADA website compliance is about making sure that everyone has equal access to all the elements on your website and apps. That may mean you need to provide alternatives for some of the functions and content on your site in order to meet ADA website compliance standards. Here’s a quick rundown of some of the accommodations that need to be incorporated into your website to meet the ADA guidelines:
Title II of the ADA prohibits discrimination against qualified individuals with disabilities in all programs, activities, and services of public entities. It applies to all state and local governments, their departments and agencies, and any other instrumentalities or special purpose districts of state or local governments. It clarifies the requirements of section 504 of the Rehabilitation Act of 1973, as amended, for public transportation systems that receive federal financial assistance, and extends coverage to all public entities that provide public transportation, whether or not they receive federal financial assistance. It establishes detailed standards for the operation of public transit systems, including commuter and intercity rail (e.g., AMTRAK).
×