var offImgArray = new Array()
var onImgArray = new Array()

offImgArray["foto1"] = new Image (512,250)
offImgArray["foto2"] = new Image (512,250)

onImgArray["foto1"] = new Image (512,250)
onImgArray["foto2"] = new Image (512,250)

offImgArray["foto1"].src = "pics/1.jpg"
offImgArray["foto2"].src = "pics/2.jpg"

onImgArray["foto1"].src = "pics/1_a.jpg"
onImgArray["foto2"].src = "pics/2_a.jpg"

function imageOn(imgName) {
if (document.images) {
document.images[imgName].src=onImgArray[imgName].src
}
}

function imageOff(imgName) {
if (document.images) {
document.images[imgName].src=offImgArray[imgName].src
}
}