How do you centre a background?

[Moh]

I used to have the code, but I cant find it.
Whats the code to center a background?
So if ur on widescreen, the center of the bg will be the same as normal screen
ty XD

[F32]

background-position?

[Moh]

<style type="text/css">
<!--
body {
    background-color: #333333;
    background-image: url(skins/habbo-plasto/bg.png);
    background-position:center;
    background-repeat:repeat-y;
    margin-left: 0px;
    margin-top: 0px;
    margin-right: 0px;
    margin-bottom: 0px;
}
-->
</style> 

Ty