Transparent Background

I just succesfully installed wordpress on my server. I am setting it up so my blog will show up in an Iframe on my webpage. What i want to do is make the background Transparent or semi-transparent so the rest of my webpage will show through on the blog. I’ve browsed other posts regarding this on this board but have been unable to get what i was looking for. I understand that i’ll have to edit the CSS stylesheet. But what do i edit to get the background on my blog transparent or adjust opacity? Does someone have a preedited CSS stylesheet that is setup like that they could post? I’ve messed around with it but was unable to get what i was looking for. Any help is much appreciated! Sorry for being such a Newbie!