var xPos=20
var yPos=document.body.clientHeight
var step=2
var delay=1
var height=0
var Hoffset=0
var Woffset=0
var yon=0
var xon=0
var pause=true
var interval
img.style.top=yPos
function changePos(){
width=document.body.clientWidth
height=document.body.clientHeight
Hoffset=img.offsetHeight
Woffset=img.offsetWidth
img.style.left=xPos+document.body.scrollLeft
img.style.top=yPos+document.body.scrollTop
if (yon){
yPos=yPos+step
}
else {
yPos=yPos-step
}
if (yPos<0){
yon=1
yPos=0
}
if (yPos>=(height-Hoffset)) {
yon=0
yPos=(height-Hoffset)
}
if (xon) {
xPos=xPos+step
}
else {
xPos=xPos-step
}
if (xPos<0) {
xon=1
xPos=0
}
if (xPos>=(width-Woffset)) {
xon=0
xPos=(width-Woffset)
}
}
function start() {
img.visibility="visible"
interval=setInterval('changePos()', delay)
}
start()