> I have stumbled over this website
> <http://www.westciv.com/style_master/academy/css_tutorial/index.html>
> and I wonder how they manage to invert the colors of the fixed
> background image when scrolling downward and the blue header moves
> away.
http://www.westciv.com/screen.css:
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;
}
#header {background-color: #091c5a;
background-image: url(images/banner.gif);
^^^^^^^^^^^^^^^^^
background-repeat: no-repeat;
background-attachment: fixed; }

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Johannes Koch
In te domine speravi; non confundar in aeternum.
(Te Deum, 4th cent.)