The Americans with Disabilities Act, the “ADA", applies to places of public accommodation. Until recently courts had consistently dismissed claims that commercial websites were places of public accommodation subject to the Act and thus legally required to be “accessible" to the disabled.
Recently, that has begun to change. Courts are no longer invariably dismissing such claims. Large and established businesses such as Target and Netflix have settled ADA claims based on the inaccessibility of their websites and have agreed to make their websites accessible.
It’s anticipated that later this year the U.S. Department of Justice will issue new regulations on website accessibility which may take a “broad view" of the ADA’s applicability to websites. See the discussions of this impending development here and here.
The Act is generous to plaintiffs’ lawyers who can recover their fees and costs in addition to statutory damages for any violation of the ADA. It’s consequently prudent to begin building accessibility into any commercial website before your business becomes a defendant.