- Hyper-Text Markup Language (HTML) provides the structure and content
- Cascading Style Sheets (CSS) determine how that content should appear visually
We often refer to this division of responsibility as the separation of concerns . By placing all responsibility for appearance on a CSS file, we can refresh the look of a web application simply by replacing the old CSS file with a new one. Similarly, we can create a new page in our site that looks and feels like the rest of the site by creating a new HTML page that links to the site’s existing CSS files.