<!--
var xPos = 20;
var yPos = document.documentElement.clientHeight; //将其中的body 换成 documentElement 文档对象
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;
document.getElementById("img").style.top = yPos;
function changePos() {
try{
width = document.documentElement.clientWidth; //将其中的body 换成 documentElement 文档对象
height = document.documentElement.clientHeight; //将其中的body 换成 documentElement 文档对象
Hoffset = document.getElementById("img").offsetHeight;
Woffset = document.getElementById("img").offsetWidth;
document.getElementById("img").style.left = xPos + document.documentElement.scrollLeft + "px"; //注意设置left 或 top 需要添加px 坐标
document.getElementById("img").style.top = yPos + document.documentElement.scrollTop + "px";

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);
}
}catch(es){
  alert(es.message);
}
}
function www_helpor_net() {
document.getElementById("img").visibility = "visible";
interval = setInterval('changePos()', delay);
}
www_helpor_net();