semi transparent / opaque browser window?

[pooka]

http://www.eq2interface.com/download...usbrowser.html

The screen shot for this mod seems to show a semi-transparent web page. After downloading the mod and banging my head against the keyboard for a while, I'm stumped. I can make all of the individual elements semi-transparent, but the browser window itself seems to want to be either on or off.

Is this a bit of css trickery that I'm missing??

*{
background-color: transparent;
opacity:.5;
}