I have upload my own image and wanted to set it as background. I follow everything it mention but the picture is not showing.
here my blog url: http://davidlee.ws/blog/
here the backgound image: http://i331.photobucket.com/albums/l...Mic/siteBg.jpg

Please advise.

Add a '/' to the start of your url so it will be
background: url(/DavidLee.ws/blog/wp-content/themes/atahualpa333/images/siteBg.jpg)