Electronic and information technology may be inaccessible to people with disabilities if it provides only one way for users to gain access to or manipulate information. For example, people who are blind cannot read instructions presented only in a visual format; people who are deaf cannot understand content that is presented only aurally; people who are color-blind cannot discriminate between color-coded options; people with specific physical limitations cannot use a software application that requires use of a mouse; people who use wheelchairs cannot operate a fax machine if the controls are positioned too high or too far for them to reach from a seated position. Many of these barriers can be lowered or eliminated when technology environments are developed from an approach called "universal design."
For more information, see the Knowledge Base article What is universal design? 
-  What is universal design?