This article, on the smashing magazine website, shows some cool tricks for working with transparency in CSS. While I am having all sorts of trouble with my CSS page, I am expecting to use these or similar tricks on my page. I recommend checking it out if you need help with transparency
On our CSS Zen Garden Sheet the transparent URL comes up repeatedly . This page gives several descriptions about what it is. Apparently, it controls background color. Which in this case, is transparent.