学步园

 <script language="javascript">
  var saveWidth = 0;
 function scaleImg(what)
 {
  what = document.getElementById(what);
   if (navigator.appName=="Netscape")
  winW = window.innerWidth;
  if (navigator.appName.indexOf("Microsoft")!=-1)
   winW = document.body.offsetWidth;
  if (what.width>(720) || saveWidth>(720)) {
   if (what.width==(720))
     what.width=saveWidth;
   else
   {
    saveWidth = what.width;
    what.style.cursor = "pointer";
    what.width=(720);
   }
  }
 }
  </script>

  <img id="img1" src="" onload="scaleImg('img1');"　onclick="scaleImg('img1');" />