The Apple Developer Connection has published a technical article on how to follow the W3C recommendations when coding web pages.
The Safari development team at Apple has made a dedicated effort to implement Web standards. This means that the easiest way to ensure optimal rendering of your pages in Safari is by following the standards. Doing so will also guarantee optimal rendering in Mozilla, Opera and Internet Explorer for Macintosh. Of course, each of these browsers has its own minor quirks or legitimate differences of interpretation, so testing your site in all of them is still mandatory. 
The article covers DOCTYPE, page layout, XHTML, CSS and Javascript. A number of external links are provided for all these topics.
http://developer.apple.com/internet/bestwebdev.html