var xPos = 20;//from hclhtt.ggxx.cc
var yPos = document.body.clientHeight;
var step = 1;
var delay = 30; 
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.documentElement.clientWidth; 
height = document.documentElement.clientHeight; 
Hoffset = img.offsetHeight; 
Woffset = img.offsetWidth; 
img.style.left = xPos + document.documentElement.scrollLeft; 
img.style.top = yPos + document.documentElement.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.style.visibility = "visible"; 
interval = setInterval('changePos()', delay); 
} 
start();