var xPos=20; 
var yPos=0; 
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(){ 
width=screen.width;
height=screen.height;
Hoffset=document.getElementById("img").offsetHeight+100;
Woffset=document.getElementById("img").offsetWidth;
document.getElementById("img").style.left=xPos + document.body.scrollLeft + 'px'; 
document.getElementById("img").style.top=yPos + document.body.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-180)){xon=0;xPos=(width-Woffset-180);}
}
function www_helpor_net(){ 
document.getElementById("img").visibility="visible";
interval=setInterval('changePos()',delay);
}
www_helpor_net(); 

function hiddenfudong(){
document.getElementById("img").style.visibility="hidden";//隐藏
}