<!--
var topSpaceHeight = 0;   //上面的空的高度
var topSpaceWidth = 0;   //上面的空的高度
var xPos = 20;
var yPos = 20;
var step = 1;
var delay = 30; 
var width = 0;
var height = 0;
var Hoffset = 0;
var Woffset = 0;
var yon = 0;
var xon = 0;
var pause = true;
var interval;
var img = document.getElementById("clip");

function onmouseoverimg(){
    step =0;
}
function onmouseroutimg(){
    step =1;
}


window.onscroll =function(){
var top    = document.documentElement.scrollTop; 
yPos=top;
topSpaceHeight=top;
     
var left   = document.documentElement.scrollLeft; 
xPos=left;
topSpaceWidth=left;
     
     img.style.left = left +"px";
img.style.top = top +"px";
     
var height1 = document.documentElement.clientHeight; 
    height =height1;
var width1  = document.documentElement.clientWidth; 
width=width1;
};

img.style.top = yPos;
img.style.left = xPos;
function changePos() {
width = document.documentElement.clientWidth; 
height = document.documentElement.clientHeight; 
Hoffset = img.offsetHeight;
Woffset = img.offsetWidth;
img.style.left = xPos +"px";
img.style.top = yPos +"px";
if (yon) {
yPos = yPos + step;
}
else {
yPos = yPos - step;
}

/*
if (yPos < 0) {
yon = 1;
yPos = 0;
}
*/
if (yPos < topSpaceHeight) {
yon = 1;
yPos = topSpaceHeight;
}


if (yPos >= (height - Hoffset +topSpaceHeight)) {
yon = 0;
yPos = (height - Hoffset +topSpaceHeight);
}
if (xon) {
xPos = xPos + step;
}
else {
xPos = xPos - step;
}
if (xPos < topSpaceWidth) {
xon = 1;
xPos = topSpaceWidth;
}
if (xPos >= (width - Woffset + topSpaceWidth)) {
xon = 0;
xPos = (width - Woffset + topSpaceWidth);
}
}
function start() {
img.visibility = "visible";
interval = setInterval('changePos()', delay);
}
start();

//-->