Think of your web page as a building. Developers who understand the purpose, strengths, and current limitations of style sheets use them to quickly create pages that display consistently across browsers and download faster.
Design pages that display consistently across browsers.
The main disadvantage of style sheets is lack of consistent browser support. Browsers earlier than Microsoft Explorer 3.0 and Netscape Navigator 4.0 don't support them at all. Higher browser versions support CSS inconsistently. It's surprising how simple this powerful tool really is. A declaration that describes how a page element should be displayed.