The Supreme Court decided under Title II of the ADA that mental illness is a form of disability and therefore covered under the ADA, and that unjustified institutional isolation of a person with a disability is a form of discrimination because it "...perpetuates unwarranted assumptions that persons so isolated are incapable or unworthy of participating in community life." The court added, "Confinement in an institution severely diminishes the everyday life activities of individuals, including family relations, social contacts, work options, economic independence, educational advancement, and cultural enrichment."
These and other types of multimedia can present two distinct problems for people with different disabilities. People who are deaf or hard of hearing can generally see the information presented on webpages. But a deaf person or someone who is hard of hearing may not be able to hear the audio track of a video. On the other hand, persons who are blind or have low vision are frequently unable to see the video images but can hear the audio track.

This title prohibits private places of public accommodation from discriminating against individuals with disabilities. Examples of public accommodations include privately-owned, leased or operated facilities like hotels, restaurants, retail merchants, doctor’s offices, golf courses, private schools, day care centers, health clubs, sports stadiums, movie theaters, and so on.  This title sets the minimum standards for accessibility for alterations and new construction of facilities. It also requires public accommodations to remove barriers in existing buildings where it is easy to do so without much difficulty or expense.  This title directs businesses to make "reasonable modifications" to their usual ways of doing things when serving people with disabilities. It also requires that they take steps necessary to communicate effectively with customers with vision, hearing, and speech disabilities.  This title is regulated and enforced by the U.S. Department of Justice. 
Because of this, among the greatest drivers of website accessibility are usability improvements and the reputation boost that it brings—or, alternatively, the lost business that organizations want to avoid as a result of inaccessible websites. According to a survey by the National Business Disability Council at the Viscardi Center, 91 percent of customers say that they’d prefer to shop at a website that prioritizes accessibility.
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.
Spector v. Norwegian Cruise Line Ltd.[64] was a case that was decided by the United States Supreme Court in 2005. The defendant argued that as a vessel flying the flag of a foreign nation it was exempt from the requirements of the ADA. This argument was accepted by a federal court in Florida and, subsequently, the Fifth Circuit Court of Appeals. However, the U.S. Supreme Court reversed the ruling of the lower courts on the basis that Norwegian Cruise Lines was a business headquartered in the United States whose clients were predominantly Americans and, more importantly, operated out of port facilities throughout the United States.
Many people with disabilities use assistive technology that enables them to use computers. Some assistive technology involves separate computer programs or devices, such as screen readers, text enlargement software, and computer programs that enable people to control the computer with their voice. Other assistive technology is built into computer operating systems. For example, basic accessibility features in computer operating systems enable some people with low vision to see computer displays by simply adjusting color schemes, contrast settings, and font sizes. Operating systems enable people with limited manual dexterity to move the mouse pointer using key strokes instead of a standard mouse. Many other types of assistive technology are available, and more are still being developed.
Aloha Tatiana! I wish your questions had straightforward easy answers – and if you are government funded it kind of is. (See here: if you are not government funded, this is something that is currently being debated in the legal system. That being said, the WCAG 2.0 guidelines are a good set of guidelines to help protect yourself if you feel you should. (You can see more on WCAG here:
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.
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.

Talk to your web designer about other techniques that will make your site more user-friendly for people with disabilities. Worried that’s not in your budget? Consider the fact that DOJ fines start at $75,000. And it's still yet to be determined if a non-compliant website is liable for one fine or will be charge per page for each violation. As the recent lawsuits illustrate, though, settlements quickly add up into the millions.

Since March 15, 2012, ADA compliance with the 2010 Standards will be required for new construction and alterations. In the period between September 15, 2010 and March 15, 2012, covered entities may choose between the 1991 Standards ADA Compliance (without the elevator exemption for Title II facilities), the Uniform Federal Accessibility Standards (Title II facilities only), and the 2010 Standards ADA Compliance.
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).