centered header img in generator? Options

[evillaundry]

firstly, here is my lj
http://---.livejournal.com
s1 generator with custom colors

alls i wanna do is center a 600x400 image at the top above the entire journal. how?

[evillaundry]

hmm. when i added that code, it just made my header image a tiling background. this is what my code looks like now:

GLOBAL_HEAD<=
<style type="text/css">
.entrybox td {
text-align: justify;
}

td, font, div, p {
font-family: tahoma, sans-serif;
font-size: 8pt;
}

body {
background-image: url(http://www.evillaundry.com/livejournal/fhmheader.png);
background-position: top;
margin-top: 400px;
font-family: tahoma, sans-serif;
font-size: 8pt;
}
</style>
<=GLOBAL_HEAD

do you see anything wrong with it? if you go to my el jay, i edited out the image link in the actual code because it looked really stupid. but the entire journal has been moved down the correct 400px, it's just that my image tiles over the entire page.