$(function() {
	$(window).resize(function () { bgScale() });
	$(window).load(function () { bgScale() });
});

function bgScale() {
	if ($(window).width()/$(window).height()>4/3) {
		$('#bg').css("width",$(window).width()+"px");
		$('#bg').css("height",$(window).width()/1024*768+"px");
		$('#bg').css("margin-left","0px");
	}
	else {
		$('#bg').css("width",$(window).height()/768*1024+"px");
		$('#bg').css("height",$(window).height()+"px");
		$('#bg').css("margin-left",($(window).width()-$(window).height()/768*1024)/2+"px");
	}
}