if (document.images) {
img99on = new Image();
img99on.src = "images/ddbytt_on.gif";

img99off = new Image();
img99off.src = "images/ddbytt_off.gif";
}

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

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