<script language="javascript">
function changeImg(mypic){
 var xw=130;
 var xl=160;

 var width = mypic.width;
 var height = mypic.height;
 
 if (width > xw ) mypic.width = xw;
 if (height > xl ) mypic.height = xl;
}
</script>
<img src="sh180.jpg" onload="changeImg(this)">

<script language="javascript">
function changeImg1(mypic){
 var xw=160;
 var xl=180;
 
 var width = mypic.width;
 var height = mypic.height;
 var bili = width/height;
 
 var A=xw/width;
 var B=xl/height;
 
 if(A>1||B>1)
 {
 if(A<B)
 {
 mypic.width=xw;
 mypic.height=xw/bili;
 }
 if(A>B)
 {
 mypic.width=xl*bili;

---------------------js---------------------------
<script language="javascript">
var xmlHttp;
var ready = false;

//创建对象
function createXMLHttpRequest(){
if (window.ActiveXObject){
xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
}else if (window.XMLHttpRequest){
xmlHttp = new XMLHttpRequest("Msxml2.XMLHTTP.3.0");
}
}

//发请请求
function doSearch(url){
createXMLHttpRequest();
xmlHttp.onreadystatechange = handleStateChange;
xmlHttp.open("GET",url,"true");
xmlHttp.send(null);
}

//处理响应
function handleStateChange(){
if (xmlHttp.readyState == 4){
if (xmlHttp.status == 200){
document.getElementById("results").innerHTML = unescape(xmlHttp.ResponseText);//用unescape()解编码