Well-designed sites contain modular elements that are used repeatedly across many dozens or hundreds of pages. These elements may include the global navigation header links and graphics for the page header or the contact information and mailing address of your enterprise. It makes no sense to include the text and html code that make up standard page components in each file. Instead, use a single file containing the standardized element that repeats across hundreds of pages: when you change that one file, every page in your site containing that component automatically updates. html, css, and current web servers offer the power and flexibility of reusable modular components, and most large, sophisticated sites are built using dozens of reusable components.