browserName = navigator.appName;
browserVer = parseInt(navigator.appVersion);

if ((browserName == "Netscape" && browserVer >= 3)||
  (browserName == "Microsoft Internet Explorer" && browserVer >=4)) version = "n3";
else version = "x";

function img_act(imgName){
  if (version == "n3"){
    imgOn = '/img/en/arrow_on.gif';
    document [imgName].src = imgOn;
  }
}

function img_inact(imgName){
  if (version == "n3"){
    imgOff = '/img/en/arrow_off.gif';
    document [imgName].src = imgOff;
  }
}