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.
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.
The guidelines are broken down by four main principles: perceivable, operable, understandable, and robust. Under each principle, there are guidelines that provide specific goals a website should work toward. Under each guideline, there are testable success criteria. Those criteria are graded A, AA, or AAA. This grade shows the level of conformity to accessibility, AAA being the highest. The law only requires A and AA guidelines to be met.