bName = navigator.appName;
bVer = parseInt(navigator.appVersion);
if      (bName == "Netscape" && bVer >= 3) version = "n3";
         else if (bName == "Netscape" && bVer == 2) version = "n2";
         else if (bName == "Microsoft Internet Explorer" && bVer >= 4) version = "n3";

if (version == "n3")
{
gammacson = new Image(); gammacson .src = "./jpg/gammas.jpg";
gammacsoff = new Image(); gammacsoff .src = "./jpg/gammao.jpg";
}

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;
}
}