<script type="text/javascript">
?? //顯示圖片
?? function over(imgid,obj,imgbig)
?? {
//大圖顯示的最大尺寸? 4比3的大小? 400 300
maxwidth=400;
maxheight=300;

?

//顯示
??????? obj.style.display="";
??????? imgbig.src=imgid.src;

???????
??????? //1、寬和高都超過了，看誰超過的多，誰超的多就將誰設置為最大值，其余策略按照2、3
??????? //2、如果寬超過了并且高沒有超，設置寬為最大值
??????? //3、如果寬沒超過并且高超過了，設置高為最大值

??????? if(img.width>maxwidth&&img.height>maxheight)
??????? {
??????????? pare=(img.width-maxwidth)-(img.height-maxheight);
??????????? if(pare>=0)
??????????????? img.width=maxwidth;
??????????? else
??????????????? img.height=maxheight;
??????? }
??????? else if(img.width>maxwidth&&img.height<=maxheight)
??????? {
??????????? img.width=maxwidth;
??????? }
??????? else if(img.width<=maxwidth&&img.height>maxheight)
??????? {
??????????? img.height=maxheight;
??????? }???????????
?? }

?? //隱藏圖片
?? function out()
?? {
document.getElementById('divImage').style.display="none";
?? }
</script>

<img id="img" src="http://www.jb51.net/images/logo.gif" onmouseover="over(img,divImage,imgbig);" onmouseout="out()" width="100" alt="" height="100" />

??? <%--顯示大圖標的區域--%>
??? <div id="divImage" style="display: none; left: 120px;top:5px; position: absolute">
??????? <img id="imgbig" src="http://www.jb51.net/images/logo.gif" alt="預覽" />
??? </div>