png transparency

http://www.misuisui.com/weblog/wap/index-wap2.php?p=2286

http://www.dillerdesign.com/experiment/DD_belatedPNG/

http://linuxtoy.org/archives/free-gimp-tutorial-pdfs.html  GIMP 教程

http://gimp-tutorials.net/gimp-vista-button

http://users.kci.net/jesse/gimp/tutorials/buttons/