var scriptsOn = false;

if (((navigator.appName == "Netscape") && (parseInt(navigator.appVersion) >= 3)) ||
   ((navigator.appName == "Microsoft Internet Explorer") && (parseInt(navigator.appVersion) >=4)))
   scriptsOn = true;

function IOn(imageName)
{
    if (scriptsOn) document[imageName].src = imageName + "2.gif";
}

function IOff(imageName)
{
    if (scriptsOn) document[imageName].src = imageName + ".gif";
}