if (document.images) {

nexton = new Image();

nexton.src = "picts/next-on.gif"

nextoff = new Image();

nextoff.src = "picts/next-off.gif"

backon = new Image();

backon.src = "picts/back-on.gif"

backoff = new Image();

backoff.src = "picts/back-off.gif"}

function img_act(imgName) {

if (document.images) {

imgOn = eval(imgName + "on.src");

document [imgName].src = imgOn;}}

function img_inact(imgName) {

if (document.images) {

imgOff = eval(imgName + "off.src");

document [imgName].src = imgOff;}}