These design tips, help all Web site visitors, not just those with disabilities. Each of the categories can be refined according to the severity of the disability. Disabilities can occur suddenly, as with an injury, or progressively as with some diseases or the aging process. Many people are born with disabilities. Situational or technological constraints can cause a person to use access methods that are common to users with disabilities.
People often have disabilities from one or more of the major categories.
Many people older than 65 experience hearing and vision loss, as well as reduced mobility. Physical disabilities include impairments of the muscles and skeletal system. Mobility, and dexterity may be difficult due to weak or paralyzed muscles, involuntary extra movement, or missing limbs. This may make using a mouse difficult or impossible, for a pointing device needs good hand-eye coordination. Impaired mouth or facial muscles may result in speech impairments, making it difficult for those with such disabilities to use speech recognition technologies.