This page uses one a background image that measures 1200px wide and repeats the ornament at about the 800px mark to achieve the appearance of a double border.
The bordered image below is a downsized version of the image used for this page's background.
Most people view the net at 1024 by 768. But it is not an overwhelming majority. There are still many people viewing at 800 by 600. As a result, we still design for 800 by 600.
This is why we create an image that works on the 800 width but overflows to fill the 1024. You could choose to create for the 1024 and let those viewing on 800 scroll.
It is possible to achieve the same appearance with CSS. Because CSS1 allows only one background image per element, you would have to apply the background image to a second element, most likely a div. Look here to see the following style applied:
body {background: #99CCFF url(images/questions.gif)
repeat-y scroll 0px 0px;}
div {background: #99CCFF url(images/questions.gif)
repeat-y 100% 100%; margin-left:100px;
margin-top:-15px; height: 1000px;}
The background image questions.gif appears below