Style sheets are actually text files that use the .CSS extension. The extension .CSS stands for Cascading Style Sheet, which refers to a style sheet's ability to overlap and overrule other style definitions.
Style sheets separate the formatting information from the topic content, so it is easier for you to design and revise your Help topics. Instead of editing many paragraphs in numerous topics to change formats, you can change the style in one place and have the change affect all topics where the style is used.
A single style sheet can be associated with any number of HTML topics. Styles are defined in style sheets. When you change a style in a style sheet, it is updated in all topics that are linked to that style sheet.
You can create style sheets and define styles from dialog boxes. There is no need for you to open the .CSS files and edit the style tags, just as there is no need for you to edit HTML code in your Help topics.
Note: Cascading style sheets were developed by the World Wide Web Consortium (W3C) and continue to evolve as a standard method for HTML presentation as Web browser technology evolves. For more information about the origins and details of cascading style sheets, visit the World Wide Web Consortium (W3C).