var scriptsOn = false;

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

function RegisterImage(imgName, imgOn, imgOff)
{
    if (scriptsOn) {
        eval (imgName + "On = new Image()");
        eval (imgName + "On.src = \"" + imgOn + "\"");
        eval (imgName + "Off = new Image()");
        eval (imgName + "Off.src = \"" + imgOff + "\"");
    }
}

function ion(imgName)
{
    if (scriptsOn)
        eval ("document." + imgName + ".src = " + imgName + "On.src");
}

function ioff(imgName)
{
    if (scriptsOn)
        eval ("document." + imgName + ".src = " + imgName + "Off.src");
}

RegisterImage ("vorigen", "vorigenr.jpg", "vorigenb.jpg");
RegisterImage ("zuruck", "backr.jpg", "backb.jpg");
RegisterImage ("weiter", "naechster.jpg", "naechsteb.jpg");