if (document.images) {
         aon = new Image(180, 55);
         aon.src = "/z-sm-a-on.jpg";
         bon = new Image(180, 55);
         bon.src = "/z-sm-b-on.jpg";
         con = new Image(180, 55);
         con.src = "/z-sm-c-on.jpg";
         don = new Image(180, 55);
         don.src = "/z-sm-d-on.jpg";

         aoff = new Image(180, 55);
         aoff.src = "/z-sm-a-off.jpg";
         boff = new Image(180, 55);
         boff.src = "/z-sm-b-off.jpg";
         coff = new Image(180, 55);
         coff.src = "/z-sm-c-off.jpg";
         doff = new Image(180, 55);
         doff.src = "/z-sm-d-off.jpg";

         }

function img_act(imgName) {
         if (document.images) {
         imgOn = eval(imgName + "on.src");
         document [imgName].src = imgOn;
         }
}

function img_inact(imgName) {
         if (document.images) {
         imgOff = eval(imgName + "off.src");
         document [imgName].src = imgOff;
         }
}