How does CSS work? When a visitor loads one of your Web pages, by either typing in the address or clicking a link, the server (the computer that stores the Web page) sends the HTML file to the visitor’s computer along with any files linked to or embedded in the HTML file. Regardless of where the CSS code is, the visitor’s browser will interpret it and apply it to the HTML to render the Web page using that browser’s particular rendering engine that is then displayed in the browser window.

Once your libraries, frameworks, and sitewide CSS are ready to go live, you need to pick the best strategy for deployment. It is always recommended that you place all your styles in one or more external style sheets, and then use either the @import code to apply them to a Web document. You have two competing priorities: