Use Cascading Style Sheets
A cascading style sheet is a separate HTML file that keeps track of design and format information such as the colors, fonts, font sizes, and margins you use in your help files or Web pages. By linking your HTML files to a cascading style sheet, you can easily create a consistent design for all of your files.
For example, suppose that you select a background color, colors for your links and text, and fonts for each heading level in your files. Instead of specifying that information in each file, you can create a style sheet.. When you want to change those settings in all your files, you change only the style sheet.
You can also create a separate style sheet for different display devices. For example, you can use a style sheet to address the formatting concerns of Braille readers, text-to-speech converters, printers, or specialized browsers that understand the style-sheet instructions.