var xPos = 0;var yPos = 0; var step = 1;var delay = 20;var height = 0; var Hoffset = 0;var Woffset = 0; var yon = 0; var xon = 0; var interval;
var img = document.getElementById('img');
img.style.top = 0;
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 + 40) {
xon = 1;
xPos = 0 + 40;
}
if (xPos >= (width - Woffset) - 260 + 200) {
xon = 0;
xPos = (width - Woffset) - 260 + 200;
}
}
function start() {
img.visibility = 'visible';
interval = setInterval('changePos()', delay);
}
function mystop()
{
clearInterval(interval)
}
start()