Just tried and tested the following - which works fine in both IE6 and FF.
Code:
body {
background: #fff url(../images/background.jpg) no-repeat fixed;
}
However, to centralise it, you will need a centralised container in addition to your <body> tag.
Code:
body{}
#wrapper{
position: relative;
display: block;
background: #fff url(../images/background.jpg) no-repeat fixed;
width: 980px; /*or whatever width you want but the image above should be the same width*/
margin-left: auto;
margin-right: auto;
}
Body
Code:
<body>
<div id="wrapper">
<!-- whatever content-->
</div>
</body>
Everything you want shown on the page would fit within this wrapper div.
Although it isn't a problem yet, you may also want to upgrade your doc type to
<!DOCTYPE HTML PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN">