CSS Question

[Brookreed]

I've been spending the morning working on my new site's CSS. Most everything is currently looking good, however there's one part of the CSS that I cannot seem to change. You can see here in the image my site. What I've been trying to do it change all the white space to a more slightly transparent color. I can't seem to find the part of the code that will change it, however. I was able to change the color of the background over it, but it won't turn transparent. So...help?