Problems with full page background

[doctorsexy]

Hi all... i am trying to make a full page background and not having much luck.

The code im trying is this but all it dose is blank out the forum...

<div id="bg">
        <img src="images/bg.jpg" alt="">
</div>

#bg {
        position:fixed;
        top:-50%;
        left:-50%;
        width:200%;
        height:200%;
}
#bg img {
        position:absolute;
        top:0;
        left:0;
        right:0;
        bottom:0;
        margin:auto;
        min-width:50%;
        min-height:50%;
}

Got this to work ... but not very well with fire fox... any help please... thanks

body {
        background: #2763B0 url(images/backgrounds/clouds2.jpg) no-repeat center center fixed;
        -webkit-background-size: cover;
        -moz-background-size: cover;
        -o-background-size: cover;
        background-size: cover;
}