Ensure all interactive features are keyboard-accessible
Director of Training
Not all people can use a mouse. Some people must use a keyboard instead, or a keyboard-like technology. Test your web site to make sure people can use all of the interactive content with their keyboards alone, without having to ever use a mouse.
People with Hand Tremors
A person with hand tremors may have a hard time making precise mouse movements, but may be able to use a keyboard to tab from one item to the next. There are even special keyboards available with raised areas in between the keys, instead of having raised keys. This allows a person with tremors to put the weight of their hand down on the keyboard, without worrying about hitting any buttons. Then they can push their finger down into the buttons to type.
Blind users may have the physical ability to use a mouse, but they can't see where the mouse pointer is, so it doesn't do them much good. They'll click on the wrong things, or on nothing at all. They would literally be pointing and clicking in the dark. Blind users rely on the keyboard instead. They listen to the output through a screen reader, and navigate web pages with keyboard shortcuts supplied by the screen reader.
Many types of physical or motor disabilities limit a person's ability to use a mouse, so keyboard accessibility is one of the most important aspects of web accessibility.