网页视口内广告浮动弹窗

<div id="img1" style="top: 21px; left: 491px;"> 
 <!--链接地址--><a href="#" target="_blank"> 
 <!--图片地址--><img src="/uploadfiles/image/logo.png" border="0"> 
 </a> 
</div>

 

<script type="text/javascript">
 var xPos = 300; //起始定位：X轴位置（居左像素） 
 var yPos = 200;  //起始定位：Y轴位置（居上像素） 
 var step = 1; //每次移动像素 
 var delay = 10; //每移1次setp所需时间（单位毫秒，1000毫秒=1秒） 
 var height = 0; 
 var Hoffset = 0; 
 var Woffset = 0; 
 var yon = 0; 
 var xon = 0; 
 var pause = true; 
 var interval; 
 var obj=window.document.getElementById("img1"); //获取DIV图层对象 
 obj.style.top = yPos + "px"; 
 function changePos(){ 
     width = window.innerWidth == 0 ? (document.documentElement.clientWidth == 0 ? document.body.clientWidth : document.documentElement.clientWidth) : window.innerWidth; 
     height = window.innerHeight == 0 ? (document.documentElement.clientHeight == 0 ? document.body.clientHeight : document.documentElement.clientHeight) : window.innerHeight; 
     Woffset = obj.offsetWidth; Hoffset = obj.offsetHeight; scrollLeft = document.documentElement.scrollLeft == 0 ? document.body.scrollLeft : document.documentElement.scrollLeft; 
     scrollTop = document.documentElement.scrollTop == 0 ? document.body.scrollTop : document.documentElement.scrollTop; 
     obj.style.left = xPos + scrollLeft + "px"; 
     obj.style.top = yPos + 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)) {xon = 0;xPos = (width - Woffset);} 
 } 
 function start(){ obj.visibility = "visible"; interval = setInterval('changePos()', delay); } 
 function pause_resume(){ if(pause){ clearInterval(interval); pause = false; }else{ interval = setInterval('changePos()',delay); pause = true;  } } 
 start(); 
</script>