鼠标移到小图上显示大图 
1 列表中显示的小图
  <img src='<%# SitePicUrl+ DataBinder.Eval(Container.DataItem, "Fieldphoto").ToString()%>' height="30px" width="50px" alt="外景小图" οnmοuseοver="ShowImage(event)" οnmοuseοut="HideImage(event)" />2 在</body>前放置一个div,也可动态创建
 <div id="ShowPicBox" class="spicDiv"><img alt="" id="ShowPic" src="" height="1px" width="1px" /></div>3 显示及隐藏的js
 <script type="text/javascript">
     var oEvent = null, oElement = null;
     function ShowImage(evt) {//显示图片用的方法
         evt = (evt) ? evt : ((window.event) ? window.event : "")
         var elem = null;
         if (evt) {
             elem = (evt.target) ? evt.target : evt.srcElement
         } //这里本来是想做ＦＦ兼容的，可是当时能力有限没有做出来．
         var ee = elem;
         var ex = ee.offsetLeft, ey = ee.offsetTop;
         while (ee = ee.offsetParent) {
             ex += ee.offsetLeft;
             ey += ee.offsetTop;
         }
         checkComplete.__img = new Image();
         checkComplete.__img.src = elem.src; 
         //这里给显示的层做定位
         ShowPicBox.style.position = "absolute";
         //ShowPicBox.style.left = ex + elem.offsetWidth + "px";        ShowPicBox.style.right =  elem.offsetWidth + 155 + "px";
         ShowPicBox.style.top = ey  + "px";
         ShowPicBox.style.display = "";
         
         checkComplete.__timeId = setInterval("checkComplete();", 20);
         elem.detachEvent("onmouseover", ShowImage);
     }    function checkComplete()//这个方法在这里检查大图是不是被加载完毕
     {
         if (checkComplete.__img && checkComplete.__img.complete)
             checkComplete.__onload();
         clearInterval(checkComplete.__timeId);
     }
     var curx = 2000; cury = 1500;
     checkComplete.__onload = function() {
         clearInterval(checkComplete.__timeId);
         var w = checkComplete.__img.width;
         var h = checkComplete.__img.height;
         //如果图片太大则按比例缩放保持图片不失真，大小在上面的curx,cury设置
         var x = 0, y = 0;
         x = w / curx;
         y = h / cury;        var m = 0, n = 0;
         if (x > 1 || y > 1) {
             m = w / Math.max(x, y);
             n = h / Math.max(x, y);
         }
         else {
             m = w;
             n = h;
         }
         ShowPic.src = checkComplete.__img.src;
         ShowPic.width = m;
         ShowPic.height = n;
         checkComplete.__img = null;
     }    function HideImage(evt) {//隐藏图片
         evt = (evt) ? evt : ((window.event) ? window.event : "")
         var elem = null;
         if (evt) {
             elem = (evt.target) ? evt.target : evt.srcElement
         }
         elem.attachEvent("onmouseover", ShowImage);
         clearInterval(checkComplete.__timeId);
         ShowPicBox.style.display = "none";
         ShowPic.width = "1px";
         ShowPic.height = "1px";
         ShowPic.src = "";
     }
 </script>