document.write("<DIV id='img' style='POSITION: absolute;z-index : 100;'> <a href='http://www.591zhekou.com' target=_blank> <img src='http://ad.sjzsw.cn/adv/images/1258788235929.jpg'  width='160'   height='80'  border='0'>  </a> 	</DIV>");

var xPos = 20;
var yPos = 10;
img.style.left= xPos;
img.style.top = yPos;
var step = 1;
var delay = 30; 
var width,height,Hoffset,Woffset;
var y = 1;
var x = 1;
var interval;
img.visibility = "visible";

function changePos() 
{
  width = document.documentElement.clientWidth;
  height = document.documentElement.clientHeight;
  Hoffset = img.offsetHeight;
  Woffset = img.offsetWidth;
  if (y) 
  {
    yPos = yPos + step;
  }
  else 
  {
    yPos = yPos - step;
  }
  if (yPos < 0) 
  {
    y = 1;
    yPos = 0;
  }
  if (yPos >= (height - Hoffset)) 
  {
    y = 0;
    yPos = (height - Hoffset);
  }
  if (x) 
  {
    xPos = xPos + step;
  }
  else 
  {
    xPos = xPos - step;
  }
  if (xPos < 0) 
  {
    x = 1;
    xPos = 0;
  }
  if (xPos >= (width - Woffset)) 
  {
    x = 0;
    xPos = (width - Woffset);
  }
  img.style.left = xPos + document.documentElement.scrollLeft;
  img.style.top = yPos + document.documentElement.scrollTop;
}

function start() 
{
  interval = setInterval('changePos()', delay);
}

function pause_resume() 
{
    clearInterval(interval);
}
start();