The web environment is flexible, with source documents that adapt to different contexts. When considering universal usability, we need to anticipate diversity and build flexible pages that adapt gracefully to a wide variety of displays and user needs.
User control
In many design fields, designers make choices that give shape to a thing, and these choices, particularly in a fixed environment, are bound to exclude some users. No one text size will be readable by all readers, but the book designer must make a decision about what size to set text, and that decision is likely to produce text that is too small for some readers. In the web environment, users have control over their environment. Users can manipulate browser settings to display text at a size that they find comfortable for reading.
Flexibility paired with user control allows users to take control of their web experience and shape it into a form that works within their use context.
Keyboard functionality
Universal usability is not just about access to information. Another crucial component is interaction, in which users navigate and interact with links, forms, and other elements of the web interface. For universal usability, these actionable elements must be workable from the keyboard. Many users cannot use a mouse, and many devices do not support point-and-click interaction. For example, nonvisual users cannot see the screen, and many mobile devices only support keyboard navigation. Some users use software or other input devices that only work by activating keyboard commands. For these users, elements that can only be activated using a mouse are inaccessible.
Make actionable elements workable via the keyboard to ensure that the interactivity of the web is accessible to the broadest spectrum of users.
Text equivalents
Text is universally accessible. (Whether text is universally comprehensible is another discussion!) Unlike images and media, text is readable by software and can be rendered in different formats and acted upon by software. When information is presented in a format other than text, such as visually using images or video or audibly using spoken audio, the information is potentially lost on users who cannot see or hear. Web technology anticipates format-related access issues and supplies methods for providing equivalent text. With equivalent text, the information contained in the media is also available as text, such as a text transcript or captions along with spoken audio (fig. 2.2).
Text equivalents allow universal usability to exist in a media-rich environment by carrying information to users who cannot access information in a given format.