canRollover=0;
browserName = navigator.appName;
browserVer = parseInt(navigator.appVersion);
if (browserName == "Netscape" && browserVer >= 3) {
   canRollover=1; // Netscape 3+
} else if (browserVer >= 4)  {
   canRollover=1; // IE 4+
}
function newimage(img,ref) {
   if (canRollover) {
      document.images[img].src = ref;
   }
}