var x = 130,y = 0
          var xin = true, yin = true
          var step = 1 
          var delay = 10
          var obj=document.getElementById("ad") 
          function floatAD() {
             var L=T=0
             var R= document.body.clientWidth-obj.offsetWidth
             var B = document.body.clientHeight-obj.offsetHeight
             obj.style.left = x + document.body.scrollLeft
             obj.style.top = y + document.body.scrollTop
             x = x + step*(xin?1:-1)  
             if (x < L) { xin = true; x = L} 
             if (x > R){ xin = false; x = R} 
             y = y + step*(yin?1:-1) 
             if (y < T) { yin = true; y = T } 
             if (y > B) { yin = false; y = B } 
          }
          var itl= setInterval("floatAD()", delay) 
         obj.onmouseover=function(){clearInterval(itl)} 
         obj.onmouseout=function(){itl=setInterval("floatAD()", delay)}