External style sheets will help you speed up the download of your Web pages. You might think that it wouldn't matter - after all, if a Web page needs the styles, the browser will download it. And yes, if your customer only ever sees one page on your site the styles will be downloaded.
But once they're downloaded, they are cached. Once your styles are cached, each subsequent page that is downloaded only requires the browser to download the HTML.
Placing styles inline or embedded in the page also requires that each page be maintained separately. So, maintaining your styles in embedded style sheets, you help your customers and keep your maintenance work down.
