var Center = new Class({
	
	initialize: function( element ) {
		this.element = $(element);
		window.addEvent('resize', function(){
			this.calculate();
		}.bind(this));
		
	},
	calculate: function() {
		var boxWidth = Number.from(this.element.getStyle('width'));
		var windowWidth = document.body.offsetWidth;
		var offset = (windowWidth - boxWidth) / 2;
		
		this.element.setStyle('left', offset + 'px');
	}
	
})