漂浮广告在ie正常,谷歌,火狐不正常,奉上100分求高人解决问题

漂浮广告在ie正常,谷歌,火狐不正常,奉上100分求高人解决问题,谢谢
代码是:

document.writeln("<div id=\"img\" style=\"position: absolute;left: 311;top:815;visibility :hidden;\" onmouseover=\"clearInterval(interval)\" onmouseout=\"interval = setInterval(\'changePos()\', delay)\" align=\"right\">");
document.writeln("<img width=\"80\" height=\"80\" src=\"\/pica/201302/20130220163926615.gif\" border=\"0\" \/>");
document.writeln("<span style=\"CURSOR:hand;\" onclick=\"clearInterval(interval);img.style.visibility = \'hidden\'\"><img border=\'0\' src=\"\/images\/close1.gif\" \/><\/span>");
document.writeln("<\/div>")


var xPos = 20;//from fiaw.net
var yPos = document.documentElement.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();

注:以上代码是放在.js的文件中,其他页面调用该js文件,页面代码有:<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">