http://www.jb51.net/article/54734.htm
<html>
<title>图片预加载</title><body><script>//判断浏览器var Browser=new Object();
Browser.userAgent=window.navigator.userAgent.toLowerCase();Browser.ie=/msie/.test(Browser.userAgent);Browser.Moz=/gecko/.test(Browser.userAgent);//判断是否加载完成function Imagess(url,imgid,callback){
var val=url;
var img=new Image();
if(Browser.ie){
img.onreadystatechange =function(){
if(img.readyState=="complete"||img.readyState=="loaded"){
callback(img,imgid);
}
}
}else if(Browser.Moz){
img.onload=function(){
if(img.complete==true){
callback(img,imgid);
}
}
}
//如果因为网络或图片的原因发生异常，则显示该图片
img.src=val;
}//显示图片function checkimg(obj,imgid){
document.getElementById(imgid).src=obj.src;}//初始化需要显示的图片，并且指定显示的位置window.onload=function(){
Imagess("http://hiphotos.baidu.com/lovebyakuya/pic/item/01cf20088f9506f063d98653.jpg","img1",checkimg);
Imagess("http://hiphotos.baidu.com/lovebyakuya/pic/item/7b7b19c70d62f4fdd0006050.jpg","img2",checkimg);
Imagess("http://hiphotos.baidu.com/joanne728/pic/item/892557641806d20eaa184c71.jpg","img3",checkimg);
}</script><img id="img1" src="loading.gif" width="100" height="100" />
<img id="img2" src="loading.gif" width="100" height="100" />
<img id="img3" src="loading.gif" width="100" height="100" />
<img id="img4" src="loading.gif" width="100" height="100" />
<img id="img5" src="loading.gif" width="100" height="100" />
</body></html>