ARIA

ARIA (Accessible Rich Internet Applications) is a W3C specification developed by WAI to make Web content and Web applications more accessible to people with disabilities. It especially helps with dynamic content and advanced user interface controls developed with HTML, JavaScript, and related technologies.

The specification, for example, allows you to add the attribute role="alert" to a <p> tag to notify a sight-challenged user that the information is important and time-sensitive (which you might otherwise convey through text color).