The Web Inspector is a tool that allows you to view information about CSS styles, DOM hierarchy and more in a compact floating window. More information about the Web Inspector can be found here.
Safari includes a develop menu that contains some tools that may be useful to web developers. The Develop menu can be enabled in Preferences under the Advanced tab.
The Page Load Test might also useful for those interested in performance. The blog has more information about using the PLT as does this page on general WebKit performance.
Working with the WebKit Nightly Builds Includes information about changes to the
- Object detection ADC article on alternatives to browser sniffing.
- XMLHttpRequest in Safari ADC article on using the XMLHttpRequest object. Includes examples.
- Web Page Development: Best Practices ADC article suggesting some best practices for web development.
- Extensive list of common user agent strings (Wikipedia)
- css-discuss Active mailing list and extensive wiki.
- Serving XHTML as text/html Ian Hickson’s article on the dangers of serving XHTML as text/html.
- Web design references Links about every topic imaginable.
- CSS 2.1 Spec When all else fails, consult the spec.