for  (var  i=0;i<document.forma.sUserName.value.length;i++)
 {
  var str=document.forma.sUserName.value;
  var intCode=str.charCodeAt(i);

  if  (intCode>=0 && intCode<=128)  {//continue;
  //字母
  }
  else  {
   //汉字
  }
 }  //end  for

document.referrer;
history.back;

1.
<script>
function check()
{
    var reg=/[^\x00-\x80]/;
    var a=document.getElementById("txt").value;
    if(reg.test(a))
    {
        alert("is 汉字");
    }
    else
    {
        alert("no");
    }
}
</script>
<input type=text id="txt">
<input type="button" value="检查" onclick="check()">
2.
<a href="javascript:history.back(-1);">返回上一页</a>

<input name="aaa" onblur="if(/^[\u4e00-\u9fa5]+$/.test(this.value)){alert('全是汉字')}">