function mouse(img,ref) { 
 browser_name = navigator.appName;
 browser_version = parseFloat(navigator.appVersion); 
 if (browser_name == "Netscape" && browser_version >= 3.0) { roll = 'true'; }
 else if (browser_name == "Microsoft Internet Explorer" && browser_version >= 4.0) { roll = 'true'; }
 else { roll = 'false'; }
  if (roll == 'true') { document.images[img].src = ref; } }