如何提前下载图片

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<HTML>
<HEAD>
<TITLE> New Document </TITLE>
<META NAME="Generator" CONTENT="EditPlus">
<META NAME="Author" CONTENT="">
<META NAME="Keywords" CONTENT="">
<META NAME="Description" CONTENT="">
</HEAD><BODY>
<SCRIPT LANGUAGE="JavaScript">
<!--
function imgGauge(imgArr){ //v3.0
  var ready=true; 
  var bgc='#9999cc'; //进度条被景色
  var okc='#888888'; //进度颜色
  var fontc='#000000'; //字体颜色
  var w=200; //进度条宽度
  var h=15;  //高度
  var yyhide=false;
  var yyshowpc=true;
  var redirection="mainF.htm";//所有图片预读结束后重定向到指定页  if (document.images)with (document){
         if (document.preloadArray==null){//first call the function 
    document.preloadArray = new Array();
    for(i=0;i<imgs.length;++i){
              preloadArray[i] = new Image;
              preloadArray[i].src =imgs[i];
            }
 }
 if(document.preloadArray){
            var howmany=0;
            for(var i=0;i<preloadArray.length;++i){
               ready = ready && preloadArray[i].complete;
               if (preloadArray[i].complete)++howmany;
            }
            var suc=Math.round(howmany*100/preloadArray.length);
            pos=Math.round(howmany/preloadArray.length*w);
            htmlcode='<body><table width='+w+' height="'+h+'" bgcolor='+bgc+' border=0 cellpadding=0 cellspacing=0><tr><td bgcolor='+okc+' width='+pos+'></td><td width='+(w-pos)+'></td></tr></table>';
            if (yyshowpc)htmlcode+='<center><font size=1 face="sans-serif" color="'+fontc+'">'+suc+'%</font></center>';
            htmlcode+='</body>';
            document.all['schedule'].innerHTML=htmlcode;
            if ((ready)&&(yyhide))setTimeout('document.all[\'schedule\'].style.visibility="hidden"',1000);
            
if(ready){
              if(redirection!='#')document.location=redirection;
    }else{
          setTimeout('imgGauge()',50);
        }
         }else{
        setTimeout('imgGauge()',1000)
     }
   }
} //这是必需的，把你准备预读到本地的图片放到数组中，注意文件名拼写正确
  var imgs=['img/bg.gif','img/bgh.gif','img/open_l.gif','img/open_r.gif','img/apple.gif','img/jiaoL.gif','img/jiaoR.gif','img/face_s.gif','img/buttons_over.gif','img/buttons_out.gif','img/scroll_out.gif','img/scroll_over.gif','img/open_l.gif','img/open_r.gif','img/finder.gif','img/mail.gif','img/IE.gif','img/music.gif','img/action.gif','img/appleX_B.gif','img/register.gif','img/ball.gif','img/color.gif','img/close_over.gif','img/close_out.gif','img/page_out.gif','img/page_over_l.gif','img/page_over_r.gif','img/counts.gif1'];
 //
//-->
</script>
</head>
<body bgcolor="#7270BC" background="back1.jpg" text="#000000" link="#000000" vlink="#000033" alink="#000033" scroll=no  onLoad=" imgGauge(imgs);">
<!-- schedule bar --> 
<div id="schedule" style="position:absolute; width:200; height:36; z-index:100; left: 328px; top: 55px; overflow: hidden; visibility: visible">
</div>
</body>
</html>