Linux Firefox doesn't look as good as Windows or Mac

Windows XP MCE


Mac OS X 10.5 Leopard


Linux - Ubuntu 8.04 LTS


As you can see, both Windows and Mac versions of Firefox 3 look great. However, the Linux version is lacking in "sex appeal". These are the default themes, you can install new themes via mozilla.com

For Mac and Windows, Firefox 3's default theme is improved over Firefox 2. However on Linux, Firefox 3 and Firefox 2 look exactly the same.