A person’s method(s) of communication are also key. For example, sign language interpreters are effective only for people who use sign language. Other methods of communication, such as those described above, are needed for people who may have lost their hearing later in life and do not use sign language. Similarly, Braille is effective only for people who read Braille. Other methods are needed for people with vision disabilities who do not read Braille, such as providing accessible electronic text documents, forms, etc., that can be accessed by the person’s screen reader program.
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.”
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."

"The United States demands that H&R Block is fined a penalty to 'vindicate the public interest' and to award money to the individuals who sued the company. The ADA prohibits discrimination of disability by public accommodations in the 'full and equal enjoyment of the goods, services, facilities, privileges, advantages and accommodations,'" the Justice Department said in joining the lawsuit.

In addition, covered entities are not required to provide any particular aid or service in those rare circumstances where it would fundamentally alter the nature of the goods or services they provide to the public. In the performing arts, for example, slowing down the action on stage in order to describe the action for patrons who are blind or have vision loss may fundamentally alter the nature of a play or dance performance.
Navigable: Content that’s repeated on multiple pages can be easily skipped. All pages have informative titles, headings, and labels that describe the page’s content and hierarchy. Navigating the page must take place sequentially, in a meaningful order that preserves relationships on the page. All link text is descriptive in order to make clear where the link will take users. If users are navigating via a keyboard, the current focus of the keyboard is always highlighted and visible.
The Federal Communications Commission (FCC) enforces regulations covering telecommunication services. Title IV of the ADA covers telephone and television access for people with hearing and speech disabilities. It requires telephone and Internet companies to provide a nationwide system of telecommunications relay services that allow people with hearing and speech disabilities to communicate over the telephone.
The Americans with Disabilities Act (ADA) was first passed in 1990. Twenty years later, the US Department of Justice released an update called the 2010 ADA Standards for Accessible Design. These standards cover the design of physical spaces and have been interpreted to include web locations as well, so it can be difficult for the would-be accessible website designer to use them.
An example is Patagonia Works, Inc. which had a complaint for a permanent injunction filed against it in the United States District Court stating, Under Section 302(b)(1) of Title III of the ADA, it is unlawful discrimination to deny individuals with disabilities an opportunity to participate in or benefit from the goods, services, facilities, privileges, advantages or accommodations, which is equal to the opportunities afforded to other individuals. 42 U.S.C. 12182 (b)(1)(A)(ii). Below is a summary of what the lawyers asked the court for. 

When you insert an image into a post or page, consider providing a rich description for the caption that will improve the reading experience for everyone, but especially folks who can’t see the image. Be creative. Instead of “My son on his swing,” try “My son is playing on his favorite swing. His face is filled with pure joy on a beautiful Spring day. Perfection.” The goal here is to convey the feeling of the image.

Level AA is a little more significant, and makes sites accessible to people with a wider range of disabilities, including the most common barriers to use. It won't impact the look and feel of the site as much as Level AAA compliance, though it does include guidance on color contrast and error identification. Most businesses should be aiming for Level AA conformity, and it appears to reflect the level of accessibility the DOJ expects. 
Thanks for writing. While I’m not a lawyer I believe if your physical practice is ADA exempt your web presence, as an extension of that physical business would maintain the same exemption status. If you’d like to be absolutely certain I’d confer with an ADA lawyer (email us, questions at yokoco dot com if you need a referral) but I don’t believe you have reason to worry.
For people who are deaf, have hearing loss, or are deaf-blind, this includes providing a qualified notetaker; a qualified sign language interpreter, oral interpreter, cued-speech interpreter, or tactile interpreter; real-time captioning; written materials; or a printed script of a stock speech (such as given on a museum or historic house tour). A “qualified” interpreter means someone who is able to interpret effectively, accurately, and impartially, both receptively (i.e., understanding what the person with the disability is saying) and expressively (i.e., having the skill needed to convey information back to that person) using any necessary specialized vocabulary.
It will annotate all the elements of a web page and point out any issues. The other tool is WAVE, which will provide you with a detailed accessibility analysis of the current page. Each tool will have its own button displayed on the bottom of your site to logged in users (you can choose which user roles will see the buttons). Just click the button of your choice to start analyzing.
Reha asked Vu if companies are obligated to comply? Vu said that unlike the physical access world, where any new building has to be compliant no matter what, there’s no such thing in the web world. The Justice Dept. hasn’t said that that’s the default, but they have said that the current regulatory regime requires it anyway. Equal access has been around since 1990.