function buttonOn (imgName) {
        if(document.images)  {
                buttonover = eval(imgName + "on.src");
                document[imgName].src = buttonover;
        }
}

function buttonOff (imgName) {
        if(document.images) {
                buttonnormal = eval(imgName + "off.src");
                document[imgName].src = buttonnormal;
        }
}