if (document.images) {

          img1on = new Image(150,53);
          img1on.src = "gif/abouton.gif";

          img2on = new Image(150,53);
          img2on.src = "gif/diron.gif";

          img3on = new Image(150,53);
          img3on.src = "gif/eventson.gif";
          
          img4on = new Image(150,53);
          img4on.src = "gif/cashon.gif";
          
          img5on = new Image(150,53);
          img5on.src = "gif/homeon.gif";

          img1off = new Image(150,53);
          img1off.src = "gif/aboutoff.gif";

          img2off = new Image(150,53);
          img2off.src = "gif/diroff.gif";
          
          img3off = new Image(150,53);
          img3off.src = "gif/eventsoff.gif";
          
          img4off = new Image(150,53);
          img4off.src = "gif/cashoff.gif";
          
          img5off = new Image(150,53);
          img5off.src = "gif/homeoff.gif";


     }

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

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