A good browser should be able to reproduce itself.
Safari 4, built entirely with valid HTML5 and CSS3. Nary an image was used (except the wallpaper, of course).
Inspired by iTunes 9, now with more WebKit - Will Norris and Opera Logo with CSS.
Intended to work in Safari 4 and Google Chrome for Mac only. Mileage in other Webkit browsers and Safari for Windows will vary. Reload button courtesy Henrik Hansen.