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

if (browserName == "Netscape" && browserVer >= 3)
  version = "n3";
else 
  version = "n2";        

if (browserName == "Microsoft Internet Explorer" && browserVer >= 4)
  version = "n3";                       
if (version == "n3") {
  nav_prodon = new Image(0, 0);
  nav_prodon.src = "images/nav_product_on.gif";
  nav_conton = new Image(0, 0);
  nav_conton.src = "images/nav_contact_on.gif";
  nav_faqon = new Image(0, 0);
  nav_faqon.src = "images/nav_faq_on.gif";

  nav_prodoff = new Image(0, 0);
  nav_prodoff.src = "images/nav_product_off.gif";
  nav_contoff = new Image(0, 0);
  nav_contoff.src = "images/nav_contact_off.gif";
  nav_faqoff = new Image(0, 0);
  nav_faqoff.src = "images/nav_faq_off.gif";
}

function img_act(imgName) {
  if (version == "n3") {
    imgOn = eval(imgName + "on.src");
    document [imgName].src = imgOn;
  }
}

function img_inact(imgName) {
  if (version == "n3") {
    imgOff = eval(imgName + "off.src");
    document [imgName].src = imgOff;
  }
}