<style>
#bg{position:fixed !important;position:absolute;bottom:0}
</stylev
<script>
window.addEvent('load', function() {resize();});
window.addEvent('resize',function(){resize();});
function resize(){
win= window.getSize();
if($('bg') !=null){$('bg').dispose();}
var bg = new Element('div',{id:'bg'}).inject(document.body,'top');
bg.setStyles({'overflow':'hidden','top':0,'left':0,'width':win.x,'height':win.y,'display':'block'});
var image = 'bg1.jpg';
var loader = new Asset.images(image, {
onComplete: function() {
var imgL = new Element('img',{src:image});
imgL.setStyles({'opacity':0});
imgL.inject(bg);
imgW = imgL.getSize().x;
imgH = imgL.getSize().y;
if(imgW/imgH>win.x/win.y){n_imgH = win.y; n_imgW = (win.y/imgH)*imgW;}
else {n_imgH = (win.x/imgW)*imgH; n_imgW = win.x;}
imgL.setStyles({'width':n_imgW ,'height':n_imgH,'display':'block','opacity':1});
}
});};
</script>