var xPos = 20;
var ybrowse = document.body.clientHeight;
var step = 1;
var delay = 40;
var height = 0;
var Hoffset = 0;
var Woffset = 0;
var yon = 0;
var xon = 0;
var pause = true;
var interval;
img.style.top = ybrowse;
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 = ybrowse + document.body.scrollTop;
if (yon) {
ybrowse = ybrowse + step;
}
else {
ybrowse = ybrowse - step;
}
if (ybrowse < 0) {
yon = 1;
ybrowse = 0;
}
if (ybrowse >= (height - Hoffset)) {
yon = 0; 
ybrowse = (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();

 







  








 
















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