学步园

<script type="text/javascript" language="javascript">

function validRegister(theform){
  var username = theform.username.value;
  var password1 = theform.password1.value;
  var password2 = theform.password2.value;
  var email = theform.password2.value;
  if(username == ""){
   alert("用户名不能为空！");
   return false;
  }
  if(password1 == ""){
   alert("密码不能为空！");
   return false;
  }
  if(password2 != password1){
   alert("两个密码不相等！");
   return false;
  }
  return true;
 }
 
 var XMLHttpReq = false;
 
 function createXMLHttpRequest()
 {
  if(window.XMLHttpRequest)
  {
   XMLHttpReq = new XMLHttpRequest();
  }
  else
  {
   if(window.ActiveXObject)
   {
    try{
     XMLHttpReq = new ActiveXObject("Msxml2.XMLHTTP");
    }catch(e){
       try{
       XMLHttpReq = new ActiveXObject("Microsoft.XMLHTTP");
       }catch(e){}
      }
   }
  }
  
 }
 
 
 function send(url){
  createXMLHttpRequest();
  XMLHttpReq.open("GET",url,true);
  
  XMLHttpReq.send(null);
  XMLHttpReq.onreadystatechange=parse;
 }
 
 
 function parse(){
  if(XMLHttpReq.readyState == 4){
   if(XMLHttpReq.status == 200){
    var res = XMLHttpReq.responseXML.getElementsByTagName("content")[0].firstChild.data;
   
    if(res == "ok"){
        document.getElementsByName("status").innerHTML="该用户名可以使用!";
     
    }else{
     document.getElementsByName("status").innerHTML=res;
     window.alert(res);
    }
   }else{
    window.alert("所请求的页面有异常！");
   }
  }
 }
 
 
 function checkUsername(){
  var username = document.getElementById("username").value;
  
  if(username == ""){
   alert("请输入用户名");
   return false;
  }else{
   send('action/checkUsername.jsp?username='+username);
  }
 }
 
</script>

注意到蓝色的代码getElementsByName如果改成getElementById则IE里面有可能出错

关于调试时可以尝试着改变getElementById和getElementsByName,互换一下有可能错误就搞定了