[SOLVED] Changing Comment Bkgd Opacity and Removing Horizontal Lines

Atahualpa 3.5.3
http://cocoamousse.com/?p=1#comment-2

I'm having a little trouble figuring out what css to place in the add html/css insert section. I want to change the caramel and mint background color opacities to match the rest of the opacities. I've tried a number of variations of:

.commentlist {
background: opacity:0.8;
}

Also, those gray horizontal lines need to go. I was able to remove them lines from the header, thanks to searching through this forum, but am having a hard time diagnosing where these are coming from.

Any help/previous post redirection would be great.
Thanks!