window.addEvent('domready', function() {   

	var bg = $('bg');
		
	Asset.image(bg.get('src'), {
		'onload' : function() {	
			bg.setStyles({
				'opacity' : 0,
				'display' : 'block'
			})
			
			var size  = bg.getSize();
			var ratio = size.x / size.y;

			window.addEvent('resize', function() {
				var wsize = this.getSize();
				if((wsize.x / wsize.y) < ratio) {
					bg.set('class', '').addClass('bgheight');
				} else {
					bg.set('class', '').addClass('bgwidth');
				}
			}).fireEvent('resize');
			
			bg.set('tween', {'duration' : 300}).tween('opacity', 1);

		}
	});

});