使用示例
<script type="text/javascript" src="http://img.sxsky.net/it/../scripts/prototype.js"></script>
<script type="text/javascript">
var progressBar;
/**//*
* 功能：admin登录
*/
function UserLogin()
{
   
    //验证页面控件
    var checkform = new CheckForm();
    if(!checkform.checkForm(document.getElementById('formLogin'))) return false;   
       
    //开始提交数据
    progressBar = new ProgressBar();
    progressBar.SetStatus("正在发送数据到服务器.");
   
    var url = "../admin.do";
    var pars = "action=Login&username=" + $F('username') + "&password=" + $F('password') + "&rnd=" +$F('rnd');
    var myAjax = new Ajax.Request(
    url,
    {method: 'post', parameters: pars, onComplete: UserLogin_CallBack}
    );
}
/**//*
* 功能：admin登录 - CallBack
*/
function UserLogin_CallBack(originalRequest)
{
  var objXml = originalRequest.responseXML;
  //alert(originalRequest.responseTEXT);
  try
  {
    if(objXml.getElementsByTagName("return")[0].firstChild.nodeValue == "true")
    {
      progressBar.isNeedConfirmButton = false;
      progressBar.isNeedProgressBar = true;
      progressBar.SetStatus("<img src='../images/error.gif' align='absmiddle'> 登录成功，正在载入，请稍候..");

      //login success
      location.href='admin_index.htm';
    }
    else
    {
      progressBar.isNeedConfirmButton = true;
      progressBar.isNeedProgressBar = false;
      progressBar.focusItem = "username";
      progressBar.SetStatus("<img src='../images/error.gif' align='absmiddle'> 对不起，登录失败！" + objXml.getElementsByTagName("msg")[0].firstChild.nodeValue);

      $('btnOK').disabled = false;
    }
  }
    catch(err)
    {
      progressBar.isNeedConfirmButton = true;
      progressBar.isNeedProgressBar = false;
      progressBar.focusItem = "username";
      progressBar.SetStatus("<img src='../images/error.gif' align='absmiddle'> 对不起，登录失败！" + err.message);

      $('btnOK').disabled = false;
    }
  }
</script>

<table width="100%" border="0" cellpadding="3" cellspacing="0">
              <tr>
                <td colspan="3" height="30"></td>
              </tr>
              <tr>
                <td width="21%">用户名:</td>
                <td colspan="2">
                  <input type="text" tabindex="1" id="username" name="username" chname="用户名" notempty="true" size="20" style="width:180px;" /></td>
              </tr>
              <tr>
                <td>密　码:</td>
                <td colspan="2"><input type="password" tabindex="2" id="password" name="password" chname="密码" notempty="true" size="20" style="width:180px;" /></td>
              </tr>
              <tr>
                <td>验证码:</td>
                <td colspan="2">
                  <input type="text" style="width:120px;" id="rnd" tabindex="3" chname="验证码" class="input_1" notempty="true" onKeyUp="value=value.replace(/[^\d]/g,'')"/>
                  <img alt="验证码" src="http://img.sxsky.net/it/../rnd.do?type=admin_rnd" border="0" usemap="absmiddle"/></td>
              </tr>             
                <tr>
                  <td class="white">&nbsp;</td>
                  <td width="22%"><input type="submit" Class="input_1" id="btnOK" value="登 录" tabindex="4"></td>
                    <td width="57%"><input type="reset" Class="input_1" value="重 置"></td>
                </tr>
                <tr>
                  <td colspan="3" height="2"></td>
                </tr>
                <tr>
                  <td colspan="3"></td>
                </tr>
        </table>

prototype.js下载http://edzh.com/scripts/prototype.js