<script>
var url=window.location.href
var str=url.substr(url.length-4,4)
if(str==".htm")
window.location.href=url.substr（0,url.length-1)
</script>

<script>   
    
  var   str   =   window.location.search；
  var   strLen = str.length；
  var   start = strLen - 4;
  if(str!="")   
  {
    var endStr = str.substr(start,4);
    if(endStr = 'html')
    {
       str = str.substr(1,strLen-1);
    }
  }
  return str;   
    
  </script>

var myReg = /.html$/;
var s1 = "adsf.htadfm".replace(myReg, ".htm");
alert(s1); 
var s2 = "adsf.html".replace(myReg, ".htm");
alert(s2);