jQuery.fn.centerScreen = function(loaded) { 
	var obj = this; 
	if(!loaded) { 
		obj.css('top', ($(window).height()/2-this.height()/2)+$(document).scrollTop()); 
		obj.css('left', $(window).width()/2-this.width()/2); 
		$(window).resize(function() { obj.centerScreen(!loaded); }); 
	} else { 
		obj.stop(); 
		obj.animate({ top: $(window).height()/2-this.height()/2, left: $(window).width()/2-this.width()/2}, 1000, 'linear'); 
	}
	return this ;
}