if(document.images) {
	
	var nav_ctw1 = new Image();
	var nav_ctw2 = new Image();
	var nav_bac1 = new Image();
	var nav_bac2 = new Image();
	var nav_nex1 = new Image();
	var nav_nex2 = new Image();

	nav_ctw1.src = "/wgbh/nova/images03/nav_ctw.gif";
	nav_ctw2.src = "/wgbh/nova/images03/nav_ctw_on.gif";
	
	nav_bac1.src = "/wgbh/nova/sciencenow/images/nav-icon-back.gif";
	nav_bac2.src = "/wgbh/nova/sciencenow/images/nav-icon-back-on.gif";
	
	nav_nex1.src = "/wgbh/nova/sciencenow/images/nav-icon-next.gif";
	nav_nex2.src = "/wgbh/nova/sciencenow/images/nav-icon-next-on.gif";

}