onscreen, via loudspeaker, via braille display) by user agents Style properties can have several origins: User agent default styles: The default style property values applied in the absence of any author or user styles. Some web content technologies specify a default rendering, others do not; Author styles: Style property values that are set by the author as part of the content (e.g. in-line styles, author style
sheets); User styles: Style property values that are set by the user (e.g. via user agent interface settings, user style sheets) supplemental content additional content that illustrates or clarifies the primary content Example 1 An audio version of a Web page . Example 2 An illustration of a complex process .