i was curious to, took me quite a long time to figure it out.
it's the whol background which they set it fixed, not only the logo. they have 2 different background, one
for the header, the other
for the main background
this is the code for the main background
body {font-size: 100%;
font-family: Verdana, Helvetica, Arial, sans-serif;
margin: 0;
padding: 0;
background-color: #fff;
background-image: url(images/page_bg.gif);
background-repeat: no-repeat;
background-attachment: fixed;
}
this one the header
#header {background-color: #091c5a;
background-image: url(images/banner.gif);
background-repeat: no-repeat;
background-attachment: fixed;
}
got it from here (screen.css)
2x simple codes, such a cool result, clever eh?