if (document.images) {
 img6_on =new Image();  img6_on.src ="/images/big1on.jpg";
 img6_off=new Image();  img6_off.src="/images/big1.jpg";
 img7_on =new Image();  img7_on.src ="/images/big2on.jpg";
 img7_off=new Image();  img7_off.src="/images/big2.jpg";

}